3.1.6 Car Stopping Distances

Question 1

List the process that one would use to find what affects the distance a trolley on a slope has on the motion of the trolley down the slope.

Answer 1

1. To investigate how the distance a trolley has rolled will affect its speed, set up a light gate, attached to a data logger, at the bottom of a slope of x angle, and a start and finish line at its beginning and end.
2. Measure the length of the trolley;
3. Mark a start line on the ramp, to make sure that the trolley always starts from the same position;
4. Measure the angel theta, and the distance from the chosen start line to the light gate d.
5. Place the trolley on the ramp, and line it up with the start line. Let it go so that its initial velocity, u=0.
6. The data logger will record the time taken for the trolley to pass through the light gate, and calculate the velocity;
7. Change the starting position of the trolley, so d is varied;
8. Repeat this experiment for each distance three times and average the record velocities to reduce error in final result.

Question 2

What are the factors in the ramp experiment that can be changed? List five of them.

Answer 2

1. The distance that the trolley travels;
2. The angle of the ramp;
3. the shape and size of the trolley;
4. The mass of he trolley (by adding weights to it);
5. The ramp material (would change this to see what effects friction has on the motion of the trolley down the ramp);

Question 3

Name the process that one would use to investigate how collisions affect the motion of the trolley, which travels down a ramp and collides with a wall. How should one analyse the results?

Answer 3

1. Set up a video camera, so that it records the experiment side-on (perpendicular to the trolley’s direction of travel);
2. Measure the length of the trolley;
3. Start recording;
4. Place the trolley on the ramp and line it up with the stat line - releasing it so that its start velocity, u=0;
5. Once the trolley has hit the wall and is at rest, stop recording;
   To analyse the results:
6. This can be used to find how the mass and velocity of a trolley can affect the resultant velocities, preceding a collision.
7. Using video analysis software, the videos can be viewed frame by frame - in reference o the metre stick, the number of frames can be counted for a trolley to pass a reference point.
8. Frames per second (the frame rate) of the video can be known. Use the equation:
   Time taken for the trolley to pass the point = number of frames for the trolley to pass a point x 1second/ frame rate of camera;

Question 4

Name the process that one would use to investigate the effects of two trolleys colliding.How should one analyse the results?

Answer 4

1. Set up two trolleys (toy cars) facing each other, on a smooth surface. The smooth surface should have a meter ruler along the side of it, indicating that the length of the surface to be 1m long. There should be a video camera perpendicular to the trolley’s direction of travel, and the smooth surface should not be at an angle.
2. Measure the length of the trolley.
3. Turn the video camera on and start recording.
4. Push one trolley so that it hits the second trolley.
5. When both trolleys have come to a stop, stop recording.
   To analyse the results:
6. This can be used to find how the mass and velocity of a trolley can affect the resultant velocities, preceding a collision.
7. Using video analysis software, the videos can be viewed frame by frame - in reference o the metre stick, the number of frames can be counted for a trolley to pass a reference point.
8. Frames per second (the frame rate) of the video can be known. Use the equation:
   Time taken for the trolley to pass the point = number of frames for the trolley to pass a point x 1second/ frame rate of camera;

Question 5

Name the biggest factor that affect how quickly a projectile will stop.

Answer 5

Initial velocity. This applies from cars crashing, to trolleys crashing.

Question 6

Define braking distance.

Answer 6

The distance the vehicle travels after the brakes are applied, until it comes to a stop.

Question 7

Define thinking distance.

Answer 7

The distance the vehicle travelsduring the driver’s reaction time.

Question 8

Name three different type of distances which affect a stopping car. How are these lined?

Answer 8

1. Braking distance;
2. Thinking distance;
3. Stopping distance;
   Thinking distance + braking distance = stopping distance.

Question 9

Name factors that affect both thinking distances.

Answer 9

Reaction time is the time that one’s body takes to react and hit the brakes after seeing a hazard. This can be affected by:

1. Tiredness;
2. Alcohol of other drug use;
3. Illness;
4. Distaractions such ass noisy children of loud music;

Question 10

Name factors that affect braking distances.

Answer 10

Braking distance depends on braking force, friction between the tires and the road, the mass and the speed.

1. Reduced friction in the tires reduces this (worn tires);
2. Badly adjusted brakes;
3. Friction between tires and the road:
   - wet or icy roads;
   - dirt on the roads;
   - wont-out tire treads;
4. Mass is affected by the size of the car and what is put into it.

Question 11

Name an equation linking thinking distance to reaction time and speed.

Answer 11

1. Thinking distance = speed x reaction time;

2. This is a simple speed, distance time rearrangement;