Physics Lab: Collisions and Braking Distance
Name: ________________________
Part 1: Inertia & Unrestrained Passenger Collisions /15 marks
Background Information:
Newton’s First Law (Law of Inertia)
 Inertia is a property of matter that measures the object’s ability to resist change in motion.
 An object in motion stays in motion until an opposing force acts on it.
 An object sitting at rest stays at rest until a force acts on it.
Importance of Seatbelts
 With no seatbelt to stop the driver with the car, the driver flies free until stopped suddenly by impact on the
steering column, windshield, etc. The stopping distance is estimated to be about one fifth of that with a seatbelt,
causing the average impact force to be about 5 times as great.

The distance that an unrestrained passenger is thrown depends on the velocity of the moving vehicle:
dthrown  v2
If the velocity doubles, the distance
that the passenger is thrown is
quadrupled (4 times greater).
Objective:

To measure the distance a passenger would be thrown if they were not wearing their seatbelts when they crash into a
barrier at different speeds.
Procedure:
1.
Set up your inclined ramp by stacking your textbooks at one end. At the other end,
position a wooden plank, binder, textbook or any sort of barrier.
2.
Using a meter stick, measure the distances as shown in the table below. At each
measurement, use masking tape to mark off correct distances. V1 should be at the
bottom of the ramp, while V5 should be near the top.
Speed units
Di s tance (cm)
V1
5.0 cm
V2
20.0 cm
V3
45.0 cm
V4
80.0 cm
V5
100.0 cm
3.
Select one hot wheel car and a passenger. Place the passenger on top of the hot wheel car so that it will sit still during the
ride down the ramp. Do not tape or attach it to the car in any way.
4.
Release the car and the passenger from each of the 5 distances. A successful collision means the passenger will be thrown
away from the car AFTER the car and passenger collides with the barrier.
5.
Mark where the passenger hits the table or floor after the collision. If the passenger BOUNCES, mark off the FIRST PLACE
that the passenger lands.
6.
Measure this distance with a ruler or meter stick a nd record it on DATA TABLE A. Do 3 complete trials to obtain accurate
results.
7.
Complete Data Table A and make a graph of Average Distance Thrown (y-axis) vs. Speed Units (x-axis). Plot your
points and use a LINE OF BEST FIT (do not “connect the dots.”)
Data & Analysis:
Data Table A. Distances Thrown After Collision (4 marks)
Speed
units
Trial #1
Trial #2
Trial #3
Distance Thrown (cm)
Distance Thrown (cm)
Distance Thrown (cm)
V1
V2
V3
V4
V5
Graph of Average DISTANCE THROWN vs. Relative Speed Units (6 marks)
Average (cm)
Conclusions: (5 marks)
1.
According to your data and graph, what can you conclude about the relationship between the speed a car travels and the
distance the passenger would be thrown? (2 marks)
2.
How is Newton’s 1 st law (of inertia) involved in this activity? Explain in detail. (3 marks)
Measuring Braking Distance Lab /14 marks
Background Information:
Factors Affecting Breaking Distance (Stopping Distance):
In order to stop a car, here are some things to consider:
1.
2.
3.
4.
5.
6.
Reaction time
Friction
Speed of the car
Mass of the car
Slope of the road
Condition of the brakes
Objective:

To measure the breaking distance of 3 different vehicles to come to a stop at different speeds
Procedure:
1.
Set up a ramp just as you did in Part 1. (See steps 1-3 in part 1)
2.
Obtain a cardboard slider. This will act as the brakes for your hot wheels cars. Above
3.
Position your slider at the BOTTOM of the ramp, so that the car will come down and hit the CENTRE of the slider.
4.
Choose ONE Hot Wheels car and weigh its MASS.
5.
Use a piece of masking tape, mark off the starting position of the SLIDER. Always return the slider to this position
afterwards.
6.
Release the car 3 times from each of the 5 positions on the ramp. After each release, measure the distance from the
starting position to where both the car and slider came to a stop .
7.
Complete DATA TABLE B.
8.
Make a graph of Average Braking Distance (y axis) vs. Speed Units (x axis). Use a line of best fit, just like in Part 1.
Data & Analysis:
Data Table B. Braking Distances at Different Speeds (4 marks)
Car # 1
Speed Units
Mass:
Trial #1 (Braking
distance)
Trial #2(Braking
distance)
Trial #3(Braking
distance)
Average (cm)
Mass:
Trial #1(Braking
distance)
Trial #2(Braking
distance)
Trial #3(Braking
distance)
Average (cm)
Mass:
Trial #1(Braking
distance)
Trial #2(Braking
distance)
Trial #3(Braking
distance)
Average (cm)
V1
V2
V3
V4
V5
Car # 2
Speed Units
V1
V2
V3
V4
V5
Car # 3
Speed Units
V1
V2
V3
V4
V5
Graph of Average BRAKING DISTANCE vs. Relative Speed Units (4 marks)
Conclusions: (6 marks)
1.
Describe the general relationship between the speed a car travels and the braking distance required. (What kinds of
patterns do you see?)
2.
How does the braking distance change with mass? (What happens if a car is heavier? Lighter?)
3.
How might a slippery surface affect the stopping distance of a vehicle?