General Physics L1 2026

[Virtual Presenter] General Physics 01/20/26. General Physics 01/20/26.

[Audio] SI Units and Measurements. SI Units and Measurements.

SI Units and Measurements.

[Audio] Giga ( G ) -1.000,000, 000 mega ( M ) 1.000.000 Kilo ( Kg ) 1000 SI Units in Prefixes hecto ( h ) - 100 deca ( da) 10 deci ( d ) - 0.1 centi ( c ) - 0.01 milli ( ml ) - 0.001 micro ( mm ) - 0.000001 Nano ( n ) - 0.0000000001.

[Audio] Length- the distance between two points. For example, the distance between Philadelphia to New York. Volume – the amount of space something occupies ( water in the container) Mass- the amount of matter in liquid, solid or gas. Weight- the force exerted by mass. - Mass and weight are not the same. - Mass is the amount of matter in an object and the weight is the force Types of Measurement applied by mass. Weight relies on gravity but mass doesn't. For example, the Moon has less gravity than the Earth so objects weight less on Earth. Mass always remains the same but weight changes. - Density- the amount of matter in the volume. Sink or float- something will sink below something that is less dense. When oil is poured into a liquid water it floats on top of the surface is less dense than water. A stone sinks into water so it is denser than the water. Water has a density about 1.0 so oil density must be less than 1 and a rock density must be greater than 1..

[Audio] Temperature- how hot or cold something Types of Measurement is- the device that measures temp is thermometer..

[Audio] Physics is the scientific study of matter, and its fundamentals constitutes on its motion and behavior through space and time and related entities of energy and force. Physics is about simplest and least complicated explanation of things- is about observing how things can work and finds the connection between cause and effect that explains why things happen. What is Physics A natural law- the rule that tells you something happens the way it does. We believe that all events in nature obey natural laws that do not change. For example, one natural law tell us a ball rolling down a ramp of certain height have a certain speed at the bottom..

[Audio] Matter- is defined as anything that has mass and take up space. Mass- is the amount of matter that make up one object. A car has more mass than a bicycle. Why- the car has more mass: the answer it that the car contains more matter. Steel, plastic and rubber are different forms of matter and the car has a lot more matter than a bicycle. Energy- Imaging dropping a stone. In your hands the Matter and Energy stone is described by its mass and the height of the ground- once is falling the stone speeds up and its height changes. The energy is how we measure the amount of change that is possible. Lifting the stone up it takes energy. Changes take energy and the amount of change you can have is limited by the amount of energy available..

[Audio] An experiment- id a situation which is set up to investigate the relationship between the variables in the system. The process to conduct an experiment is called Scientific method. Experiments usually have a question associated with them. An example – how does the steepness of the ramp effect the speed of the ball at the bottom. To answer the question you do an experiment to measure Investigating Systems the cause and effect relationship between the ramp angle and the speed of the ball. The variable that is the cause of change in the system is called the independent variable. This is the variable that you change in an experiment. The ramp angle is the independent variable. The variable that slow the effect of those changes is called the dependent variable. The speed of the ball is dependent variable..

[Audio] Hypothesis – is an educated guess that predicts the relationship between the dependent and independent variable in an experiment. Designing experiments- is an ideal experiment where you change only one variable at a time. Investigating Systems A variable that remains the same is called the control variable. The variable that is changed is called an experimental variable..

[Audio] When you want to understand something, you focus your attention on a small group called the system. A system- is group of objects that effect variables that are related. You choose the system to include things you wish to investigate and exclude things you think that are not relevant. Variable – is a factor that effects the behavior of the Systems and Variables system. For example – imagine you are doing an experiment with a car rolling down the ramp. The car and the ramp are variables in the system. The car speed is an important variable. Time, position and mass are other variables..

[Audio] Speed- is the measure of the distance traveled in each amount of time. Speed is distance divide by time or S= D/T Therefore, to calculate the speed of an object you must know two things: the distance traveled by the object and the time it took to travel the distance. Calculating Speed Speed is calculated by the dividing the distance by the time taken. For Example- If you drive 150 km in 1.5 hours than the average speed of the car is 150 km / 1.5 hr which is equal to 100 km/ hr..

[Audio] 1- A family traveled from New York to Philadelphia at one average speed of 60 km/hr for total of 2 hours. How far they travel? We are looking for the distanceFormula for Distance is: D= S X T D= 60 km/h x 2 hr= 120 km. 2- Calculate the distance that you travel if you were driving for 3 hours at 70 km/hr. Calculate SpeedDistance – Time D= S x T D= 70km/hr x 3 hr = 210 km..

[Audio] 3- A car travels 150 km in 3 hours find the speed of the car? S= D/T S = 150 km/3hr= 50 km/hr. 4- A bus travels 252 km at 72 km/hr. How many hours did it travels- we are looking for time. Formula for time is: T = D/ S T= 252 km/ 72km/hr= 3.5 hours. Calculate SpeedDistance – Time 5. How long does it take to travel 180 km at 45 km/hr- Solve for time. T = D/S T= 180 km /45km/hr= 4 hr..

[Audio] Speed- is a scalar quantity that refers to how fast an object moves. Units of speed Units for measurement for speed are: km/hr, min/ sec, cm/sec and mm/sec..

[Audio] Models Consider the following: a stretched rubber band is used to launch a car along a track that is straight for a distance and then turn uphill. If the rubber band is stretched more the ahs more speed – if the car has more speed, it gets higher on the hill. What is the Model- a model is an explanation that links the variables in the system through cause and effect. The model is for the car and the ramp. Tracking a car gives energy due to its speed, climbing in the hill takes energy. This explanation is a model that links the height and speed through idea of energy..

[Audio] Is easy to recognize when an object is in motion and also when an object is at rest. Examples- car is moving, plane is flying are ex- of motion. An example of objects at rest will be pencil stay unouched in the table. The question is what causes an object to move the answer will the force. Newton First Law of Motion Force- is any influence that causes an object to change it shape or motion. Examples- you must apply force to move heavy objects, or if you press the a spheric clay it changes its shape – due to application of force..

[Audio] Newton's first law of motion also called law of inertia, states that an object at rest remains at rest and an object in motion remains at motion with the same velocity unless acted by an unbalance force. Velocity – is the speed of object in a specific direction. Newton's First law of Motion An Unbalanced force is an external force that change the motion of an object. Balance force- when an object is at rest or moving at constant velocity are the forces that are balanced..

[Audio] Example- take a cup of coffee sitting on the table. The force of gravity pulling down is balanced by the force of kitchen table, and also we have an upward force which is trying to keep it balanced. If you want to move the cup of coffee, you must apply an external force to disrupt the balance. Another example of Newton first law is the jumping free fall of a paratrooper from a plane. Few examples of Newton 1 law When he jumps the downward force of gravity pulls toward the center of the earth. At the same time the paratrooper experiences an upward force of air resistance. He experiences two forces: 1- force toward the earth and 2- the force of air resistance..

[Audio] When the paratrooper open the parachute, something happens. The parachute increases the surface area. Air resistance of the parachute increases as he falls – in this case the downward and upward force becomes equal. In this example, the paratrooper starts falling toward Earth at a uniform velocity to execute his journey safely. Uniform Velocity- also known as terminal velocityboth downward force and upward force are equal. Uniform velocity and Inertia Why he still coming down and both forces are equal the answer inertia..

[Audio] Inertia- is simply the resistance to change in motion. In short objects tends to keep doing what they already been doing. Example- when you travel in the car you suddenly apply the brake when you do that you feel the forward push. It is because you were in motion in foreword direction. So inertia of your body try to maintain your state of motion in foreword direction as a result you feel a forward push. Inertia Pound - is the unit of force. When you measure weight in pounds on a scale you also measure the force of gravity. 1 pound- ( lb)- is the force exerted by gravity on a mass of 0.454 grams..

[Audio] Newton ( N ) – is the metric unit of force. One newton is the force it takes to change the speed of 1kg of mass by 1 m/s. Newton ( N ) Net force- is used to describe the total of all forces on an object. Th net means total. Example – if two people are pushing two boxes so each box weight about 300 N each. 300N + 300 N = 600 N..

[Audio] Newton thought that what will happen if net force is not equal to 0. In this case Newton presented 2- law of motion. We know that if the ball is at rest position the ball is at natural state and the net force will be always 0. If the car is at uniform motion is also at natural state and the net force is 0. Neaton states that- if we exert force at the stationary ball force will change its velocity. For example- the velocity of the ball was at V= 0m/s after exerting force it's velocity changes to V= 5 m/s. We must know that when velocity changes the acceleration produces. So indirectly Newton states that when the net force is not equal Newton 2Law of Motion to 0 it produces acceleration. Newton 2- law- relate the net force on an object, the mass of the object and acceleration. It states that the stronger the net force on an object the greater the acceleration. Formula for Newton 2- law is: F = m x a. ( m- mass , F- force , a- acceleration)..

[Audio] Example- if we one truck with uniform motion the net force is equal to 0 N. After you apply some force to the pedal the truck will stop. So Newton states that the force changes of the car when it stops. Example- let the initial velocity of the car Newton 2law was at V= 30 m/s after exerting some force the velocity of the car will be at V= 0 m/s because you apply the brake and the car it did stop. Here velocity changes and also we know that when velocity the acceleration produces. According to Newton when the net force is not equal to 0 it produces acceleration. Therefore, acceleration is directly proportional to the mass of the body..

[Audio] 1- Consider on car and the truck. The mass of the car is 100 kg and the mass of the truck is 200 kg. Lets exert or push force of 200 N in the car and also 200 N force at the truck. We will observe that the car will accelerate at a= 2 m/s and the truck will start moving at acceleration of a= 1m/s. 2- A object with mass of 2.0 kg accelerates 2.0 m/s when an unknown force is applied to it. What is the amount of force: Problems with F= m x a m= 2 kg a = 2.0 m/s F= ? F= m x a F= 2kg x 2. 0 m/s = 4N.

[Audio] Problems with N- 2 law. Problems with N- 2 law.

[Audio] 5- AN object with mass of 2.0kg has a force of 4.0 N applied to it – what is the resulting acceleration of the object? Problems F= ma m= 2.0 kg F= 4.0N a= ? 4N /2 kg = 2m/s/s..

[Audio] Newton Second Law and Acceleration Acceleration – is how motion changes. The amount of acceleration depends both on force and mass, and Newton 2- law also relates to force, mass and acceleration. Example with- acceleration – what happens if you coast on a bicycle down a long hill without pedaling at the top of the hill you move slowly – as you down hill speed gets faster and faster- you accelerate. Acceleration- is the rate at which your speed increases..

[Audio] Positive and Negative Acceleration If an object speeds up it has positive acceleration. If it slows down it has a negative acceleration. In physics the word acceleration refers to any change in speed- positive or negative. Sometimes we use the word deceleration to decrease the motion that is slowing down. Units of acceleration- speed units and time units- we can use an example of the sport car in which acceleration will be given in kilometers, per hour, per speed- so this units can be expressed as: km/hr/s.

[Audio] Formula for acceleration a= Vf- Vi/t ( Vf- final velocity, Vi- initial velocity, t – time , a- acceleration. The cause of acceleration is force. Force causes acceleration- unbalanced forces acting on an object that can cause the object to accelerate. Newton second law- relates the net force acting on an object to its mass an acceleration. It also states that the greater the net force on an object the greater it is his acceleration..

[Audio] Forces causing acceleration When a hockey puck is at rest net force it is balanced so the puck is at equilibrium state. Hit the puck – will create an unbalanced force- and the puck experiences a change in motion – it accelerates. Apply another force by striking the puck again the puck motion changes again. Example- if you have a car at point A we know that car is at rest the initial velocity Vi= 0 m/s, and if the car is moving to the point B its motion will be V= 12 m/s so the velocity of the car has gained to the time to t= 3 sec. a= vf-vi/t a= 12 m/s – 0m/s divided by 3 s = 4 m/s/s..

[Audio] 2- a cyclist speed up from 2 m/s to 4 m/s in a straight line in 2 sec calculate his acceleration. a= Vf- Vi /t Problems a= 4 m/s – 2 m/s : 2 = 1 m/s /s. with acceleration 3- A car starts from rest and accelerate to a velocity of 25 m/s in two minutes what is the acceleration. a = 25 m/s – 0 m/s : 120 s a= 0.21 m/s/s..

[Audio] 4- A horse starts his race from starting gate at rest ( Vi= 0m/s ), and then she accelerates 10 m/s for 13 seconds. How fast the horse will be going? a = Vf- Vi /t Acceleration Problems a = 10 m/s – 0 m/s : 13 s a = 130 m/s..

[Audio] Free fall Gravity and free fall- Imagine dropping a baseball out of second floor window- what happens? Of course the ball falls toward the ground. If it accelerates at what rate – do all objects fall at same rate? and Upward launches The acceleration due to gravity- on object in free fall- is it is accelerating due to the force of gravity and no other forces acting on it. A dropped ball is in free fall from the instant it leaves your hand until it reaches the ground. A ball throw upward is also in free fall after it leaves your hand. Birds, helicopters, and aiplanes are not normally in free fall – because forces other then gravity acts on them..

[Audio] Objects in free fall accelerate at 9.8 m/s/s which also noted as ( g ), which also acceleration due to gravity. The Speed in free fall- if you know the acceleration of an object in free fall you can predict its speed at any time after it dropped. The speed of a dropped object will accelerate by 9.8 m/s every second. acceleration due to gravity So if it start at rest it will be moving at 9.8 m/s after one second will be 19.6 m/s after 2 seconds will be 29.4 m/s and after three seconds and so on. Free fall formula is V= g x t.

[Audio] Upward Launches If you through the ball upward will slow down -as it moves upward come to a stop for an instant and then falls back down. As it moves upward the speed decreases by 9.8 m/s every second until it reaches zero. The ball then reverses direction and starts falling down. As it falls down the speed increases by 9.8 m/s every second..

[Audio] Velocity in Upward launches When an object moves direction is important in this case we use velocity instead of the speed. Velocity- is speed with direction. According to the figure 2.12 in page 40 the ball initial velocity is + 19.6 m/s and its velocity for second later is – 19.6 m/s. The positive sign means upward and the negative sign means downward..

[Audio] Free fall and Distance Average speed- one way to calculate distance is to use the average speed. In free fall an other situation of constant acceleration the average speed of the starting or initial speed ( Vi) and the final speed ( Vf). Taking the average account for the fact that the speed is not constant. Average speed formula is V avg= Vf- Vi : 2 Example- a rock falls of a cliff and splashes into a river 5 seconds later. What was the average speed during its fall. Vf= gt and Vavg = Vi + Vf /2. Solution Vf= 9.8 m/s x 5 sec = 49 m/s Vavg = 0 + 49 m/s : 2 = 24.5 m/s..

[Audio] Gravity and Weight Gravity force depends on mass- The force of gravity on an object is called weight. The symbol Fg stands for force of gravity and is used to represent weight. AT Earth surface gravity exerts a force of 9.8 N on every kilogram of mass This means that 1 kg mass has a weight of 9.8 N, a 2 kg mass has a weight of 19.6 N and so on. On Earth surface the weight of any object is its mass multiplied by 9.8 N/kg. Because weight is force it is measured in units of force such newtons and pounds..

[Audio] Weight and mass We tend to use weight and mass interchangeably. People and things such as food are weighted in kg and pounds. If you look on the label of a bag flour it lists the weight in two units: 5 pounds in English units and 2.3 kg in SI units. As long as we are on Earth where g = 9.8 N/kg a 2.3 object will weight 5 pounds. But on Moon the g= 1.6 N/kg so 2.3 kg will weight only 0.8 pounds in Moon. Formula for weight is Fg = mg.

[Audio] Problems with Fg= mg 1- Tom has a mass of 62 kg what is the force of Tom due to gravity? Fg= mg = 62 kg x 9.8 m/s/s = 607 . 6 N What is Tom weight F = W ( same as force) 607. 6 N 2- The gravitational force exerted on an object on Earth is 800 N – What is the mass of the object? 800 N / 9.8 N/kg = 81.6 kg..

[Audio] Is all about the physical interaction between two objects. Example- when you sit on chair, your body exerts a downward force on the chair which can be F= 600 N. At the same time, the chair also exerting one upward force with F= 600 N on your body. Due to physical interactions between your body and the chair two forces are generated. These two forces are called action and reaction forces. Newton's Third Law of Motion ( test 2 starts here) Newton's law states that: for every action there is an equal and opposite reaction. For example, the magnitude of downward action and the magnitude of upward reaction is the same but both have opposite direction..

[Audio] Consider a moving airplane – we know that engine of an airplane forces the air in a backward direction, which is an action. As the result of this action airplane will move forward direction which is one reaction. When we walk in the ground out foot exerts backward force on the ground which is an action. As a result, the ground exerts force in our body in the forward direction which is one reaction. Application of Newton's 3rd- law in daily life Consider launching a rocket- rocket engine produces downward force which is an action – the expanding gas particles pushes against the rocket. As a result, an upward thrust is produced which moves the rocket in upward direction as reaction..

[Audio] In comparison with 1 and 2 law the third law deals with pairs of objects this is because all forces came in pairs. A skateboard contest- all forces come in pairs when you push the ground ( action ) the reaction of the ground pushing back on your foot it what makes you move. Action is your pushing on the ground and the reaction is ground pushing on you. Imagine you have the Elephant and Newton in the Newton's Third law – Skateboard contest skateboard. They can only push against each other not against the ground. The elephant knows it is much stronger and pushes off Newton with a huge force thinking it will surely win. Newton wins- no matter how hard the elephant pushes Newton always move away at greater speed. Why- Newton accelerates more because his mass is smaller..

[Audio] Both are always there whenever any force appears They always have the same exact strength They always act in opposite direction Action and Reaction Forces Both are real forces and either or both can cause acceleration..

[Audio] Let's consider two objects are falling from the height of 200 meters. Let the mass of one object be 5 kg and the mass of the other object be 50 kg. That's assume that these two objects accelerate toward the earth at the same speed. If you are asked to catch up these two objects which one is the possibility to catch up first. Of course, the object that has smaller mass you select first or pick up first. Momentum of 5 kg is less than 50 kg body. Momentum Formula – P = mv In physics we define momentum as : momentum is cross product of mass and velocity. We denote momentum by letter ( P ) – momentum Formula P = m x v ( m- mass , v – velocity)..

[Audio] Momentum is a vector quantity and also the velocity is vector quantity. Direction of P is the same as direction of V – velocity. Momentum The SI Unit of mass is Kg and the SI unit for velocity is m/s and SI unit for momentum P is P= kgm/s..

[Audio] How we can calculate the P ( momentum ) of an object In case 1- the person is standing on the road and suddenly the mass of one bicycle which 50 kg coming toward him wit the velocity of 60 m/s. In this example if this person got hit he most likely will be injured? In case -2- consider the same person standing on the road and suddenly he got hit by a truck with the mass of 2500 kg with the velocity of 60 m/s in this case most likely will die. In case 1 P= mv m= 50 kg V= 60 m/s P = mv P= 50 kg x 60 m/s = 3000 kgm/s..

[Audio] Momentum Practice Case- 2 m= 2500 kg V= 60 m/s P= 2500 x 60 m/s P= 150,000 kgm/s.

[Audio] Does the stationary object possess momentum Let's assume the car standing at rest with mass m= v=0 m/s P=mv P= mx o m/s P= ok m/s It shows that the object is at rest its momentum will be 0. 2- What is the momentum of white bird with a mass of 0,04 kg flying at 19 m/s. P= mv P= 0.04 x 19 = 0.76 kgm/s..