Task about a Car - Lab Report Example

1. You are traveling in a car going at a constant speed of 100 km/hr down a long, straight highway. You pass another car going in the same direction which is traveling at a constant speed of 80 km/hr. As measured from your car’s reference frame this other car is traveling at -20 km/hr. What the acceleration of your car is as measured from the other car’s reference frame? What the acceleration of the other car is as measured from your car’s reference frame? Give an explanation for your answers.

Solution

In this case, you need to consider the relative velocity with respect to the car you are traveling in.

Therefore relative speed with reference to the car you are traveling in= 100-80=+20 km/h. the fact that you are traveling at a constant speed means that the acceleration is equal to zero.

Note that in the computation of acceleration,

In the second reference frame, the relative speed=80-100=-20 km/h. In this case, too, the velocity is constant and hence the acceleration is equal to zero.

In both cases, the car accelerates but the passengers (you) do not accelerate because the car is being used as the reference moving frame.

2. 
   Consider the following three cases.
   a. You try to push on a large box that has a mass equal to your mass across the floor. However, the box does not move due to friction. How do the magnitudes of the forces between you and the box compare to each other?

Solution

The magnitude of the force holding the box onto the surface is higher as compared to that applied to move the box. This explains the reason why the box remains on the surface and does not move. The force of friction is dependent on the total force that is pressing the two surfaces together.

b. You switch to a box that has a mass that is half of your mass and try to push it across the floor, but it also does not move. How do the magnitudes of the forces between you and the box compare to each other?

Solution

The magnitude of the force holding the box onto the surface is lower as compared to that applied to move the box. This implies that the resisting force (friction) is lower than the force that is applied to start motion and this causes the box to remain on the surface without any motion towards any of the directions. For motion to occur, the two forces must have equal magnitudes.

1. 
   You are able to place the box that has a mass half of your own onto a platform with wheels and you are able to push the box across the floor. How do the magnitudes of the forces between you and the box compare to each other?

Solution

The magnitude of the force holding the box onto the surface is equal to the force of friction. The wheels reduce the resisting force (friction) between the floor and the box and hence the box is able to slide across the floor. Once the two forces have equal magnitudes, the box is able to slide across the floor.

3. 
   You apply a 2 Newton force to a 0.5-kilogram cart on a track and measure the acceleration of the cart with a motion detector. The acceleration is measured to be equal to 3.5 meters/sec2. Calculate the frictional force. In which direction compared to the applied force is it directed?

Solution  

To compute the frictional force we must apply the following.

The force is in a direction opposite that of the applied force.

4. 
   You are back in your car and are driving at a constant speed around a curve. Use Newton’s 3 laws to describe this situation.

Solution

Newton’s third law states that for every force that is applied, there is a resultant reaction force that is equal in magnitude but opposite in direction of the applied force.  In this case, the speed of the car is constant and it is only the direction of motion of the car around the curve that is changing. This results in a change in the radius vector which is shown by.  The fact that you are driving at a constant speed means that you may not experience a change in acceleration.