Velocity

Velocity is the displacement (change in position) of an object per unit time. Velocity can be calculated by dividing the displacement travelled by an object by the time it took to do it. If an object were to go the same displacement over the same time every time then it is called constant velocity. Not everything moves in with a constant velocity so the formula can be written as the second displacement subtract the first displacement divided by the second time subtract the first time. This means that average velocity equals to change in displacement divided by change in time. Another kind of velocity is Instantaneous Velocity. Instantaneous Velocity is the velocity of an object at a specific point in time. The velocity of an object can also be found from a displacement vs. time graph by taking the slope of the line or by taking the slope of a tangent if it is a curve.

An example of velocity on car:

Two places are linked by a straight highway of 200km. A car goes from place 1 to place 2 in 3 hours. We can calculate the velocity of the car:

Displacement = 200km x 1000 = 200 000m

Time = 3h x 3600 = 10800s

Velocity = Displacement / Time

Velocity = 200 000m / 10800s

Velocity = 18.5m/s

Therefore the car travels at 18.5m/s for 3 hours to get to its destination. The unit for velocity is m/s because the displacement is in meters and the time is in seconds and they are both being divided.

Cars use speedometers to check the speed that they are travelling at. The first speedometer created was by a man named A.P. Warner who was the founder of Warner Electric Company.

Friction

Friction is a force that opposes the motion when ever one surface moves or tends to move with reference to another. There are different kinds of friction such as: Sliding Friction, Rolling Friction, Limiting Static Friction, Fluid Friction and Kinetic Friction. Sliding Friction is the friction that makes it difficult for an object to slide this friction helps us turn corners without sliding. Rolling Friction is the force that is opposing an object that is rolling such as a ball over grass. Fluid Friction is a kind of friction that is caused by a fluid pushing against an object. Limiting Static Friction is the maximum amount of friction just before an object at rest starts to move. The last kind of friction is kinetic friction this kind of friction is the force that opposes the motion of an object after it is moving. Friction is necessary because without it objects in motion will remain in motion.

Gravitational Potential Energy

Gravitational Potential Energy (GPE for Short) is the energy that an object has because of the distance from earth. GPE can be calculated using the formula GPE = mgh. This formula can be derived from the formula for work which is W = Fd. Work equals force multiplied by the distance and force can stand for mass multiplied by the gravitational field intensity which is 9.8 on earth. Now if we assume that there is no friction then work can equal to gravitational energy meaning we can say that GPE equals to mass multiplied by gravitational field intensity multiplied by distance which can be replaced by height.

 Here is how GPE can be applied to cars:

A 1500kg car is on top of an object 3.0 m about to jump off. Calculate the GPE of the car just as it drives of the object.

Mass = 1500kg

Gravitational Field Intensity = 9.8 N/Kg

Height = 3m

GPE= mgh

GPE = (1500) (9.8) (3)

GPE = 44 100J

Therefore that car has 44 100J of potential energy at that height on earth. A measuring tape was used to measure the height of the object. The modern measuring tape was invented by Alvin J. Fellows.

The Speed of Sound

Although we may use some number to represent the speed of sound the actual speed of sound is different in different places. The speed of sound varies with the temperature of the air. Warmer air means the molecules in the air are moving quickly this also means that the speed of sound increases and the same goes for cold temperature. As the temperature cools down the speed of sound gets slower. The speed of sound at 0 degrees Celsius is 331 m/s. There is an increase in .59 m/s for every 1 degree increase in temperature. This means that the speed of sound in any temperature can be calculated by the formula v = 331 + 0.59T where v is the speed of sound and T is the temperature.

The graph above compares the temperature with the velocity of sound. As the graph shows there is a constant change in velocity as there is a constant change in temperature. An example of a car using sound is when it honks:

It is -30 degrees Celsius outside and a car honks at a person. How fast was the sound waves traveling going to the person?

Temperature = -30 degrees Celsius

Speed of sound at 0 Degrees Celsius = 331m/s

Change in meters per seconds per 1 degree increase = 0.59 m/s

v = 331 + 0.59(Temperature)

v = 331 + 0.59(-30)

v = 313.3 m/s

Therefore at -30 degrees when the car honked at the person the sound travelled at 313.3 m/s. The invention of the car horn is credited to Miller Reese. Now days the horns just come with the cars so there is no special company that sells them.

Power

Power is the rater at which work is done. Power can also be put as the rate at which energy is used up. Factors that effect power are work done and energy consumed in the time taken. Power can be calculated by dividing the work done or the energy consumed by the time taken. Since energy and time are both scalar power is also scalar. The unit for power is joules per second which is known as Watt. Power can also be related to speed by the formula Power equals force multiplied by average velocity.

 A power example that relates to cars is:

A car accelerates from 0 to 28m/s this is a rate of 5.0 m/(s x s). The total force of friction on the car is 650N. Calculate the power of the engine if the car has a mass of 1450kg.

v1 = 0

v2 = 28 m/s

Average Speed = 14 m/s

a = 5 m/(s x s)

m = 1450kg

Ff = 650N

F(net) = 1450(5)

F (net) =7250N

Force Applied = F (net) – Ff

Force Applied = 6600N

P = Fv

P = (6600) (14)

P = 92400 W

Therefore this engine gives a power of 92 400W. The first engine was invented by Beau de Rochas who had invented a 4 step combustion engine. The engines in cars are made and put in by the car manufacturers so we don’t have to go buy them our self.

Mass and Force of Gravity

Mass is the amount of material in an object. The mass of an object does not change no matter where you are. If you’re on moon your mass is still the same as if you’re on earth. Force of gravity is the force of attraction between any two masses in the universe. The weight is the amount of force that a celestial body exerts on a mass. The weight of an object can be found based on the mass of the object multiplied by the force of gravity acting on it.

This can be applied to a car as such:

A car has a mass of 150kg find the weight of the car on earth and on moon. When the force of gravity on earth is 9.8 N/Kg and the force of gravity on the moon is 1.62 N/Kg.

m = 150kg

Gravity (earth) = 9.8 N/Kg

Gravity (moon) = 1.62 N/Kg

Weight on Earth = 150 (9.8)

Weight on Earth = 1470N

Weight on Moon = 150(1.62)

Weight on Moon = 243 N

Therefore the weight earth will be 1 470N and the weight on the moon will be 243. You can find out your mass by standing on a weighing scale. Weighing scales were invented long time ago but they were just of different kinds. Different companies can sell these scales and it does not really matter where you get them from.