P8.1 - Physics On The Move

Question 1

What is the speed measuring system for a 100m sprinter?

How would you also measure the distance and time?

Answer 1

Speed measuring system - Electronic timing.
Example of how you measure the distance - Measuring tape/Trundle wheel.
Example of how you measure the time - Pressure sensor to start and break laser beam at the end.

Question 2

What is the speed measuring system for a car on a road?

How would you also measure the distance and time?

Answer 2

Speed measuring system - A speed camera
Example of how you measure the distance - A trundle wheel to find the distance between marks on the road
Example of how you measure the time - Time between two photos

Speed measuring system - A speed gun (LIDAR)
Example of how you measure the distance - Use distance = (Speed x Time taken for a reflection)/2
Example of how you measure the time - Time between pulses

Question 3

What is the speed measuring system for a cyclist?

How would you also measure the distance and time?

Answer 3

Speed measuring system - A wheel sensor
Example of how you measure the distance - Wheel diameter
Example of how you measure the time - A magnetic sensor detects one rotation

Question 4

What is the speed measuring system of anything?

How would you also measure the distance and time?

Answer 4

Speed measuring system - Satellite navigation (satnav)
Example of how you measure the distance - Comparing the distance to three satellites
Example of how you measure the time - Electronic timer

Question 5

What is the typical speed in m/s for a:
A) A person walking
B) A person running
C) A person cycling
D) An Olympian cycling
E) Strong wind
F) A car
G) A train
H) Sound

Answer 5

A)1 m/s
B)5 m/s
C)7 m/s
D)20 m/s
E)13 m/s
F)22 m/s
G)56 m/s
H)343 m/s

Question 6

What is the typical human reaction time?

Answer 6

0.2 seconds

Question 7

What is the thinking distance?

Answer 7

The distance that a car travels while the driver reacts to a hazard.

Question 8

What factors affect thinking distance?

Answer 8

• Age (Reaction time increases as you get older).
• Drinking alcohol.
• Using drugs, as well as some medicines
• Being tired.
• Distractions such as other people in the car or using a radio or satellite navigation system.

Question 9

What is braking distance?

Answer 9

The distance that a car travels while the driver is braking.

Question 10

How do you calculate stopping distance?

Answer 10

Stopping distance = Thinking distance + Braking Distance

Question 11

What factors effect braking distance?

Answer 11

Factors that affect the car such as:

• The weather
• Worn tyres
• Faulty brakes
• Badly maintained roads

Question 12

What is the relationship between stopping distance and speed?

Answer 12

Stopping distance increases rapidly with speed.

Question 13

What acceleration does the highway code assume for stopping distance?

Answer 13

-6.6m/s

Question 14

How might a seatbelt injure you when your deceleration (negative acceleration) is very large?

Answer 14

• The seatbelt can cause compression injuries.
• Your internal organs can be injured because they continue to move inside your body even if your ribs are stopped by the seatbelt.

Question 15

What happens if the acceleration you experience is about twice the acceleration due to gravity?

Answer 15

You feel a force equal to twice your weight, which people sometimes call ‘2g’.

Question 16

Why do seatbelts need to stretch?

Answer 16

It increases the time of collision and hence the rate of change of momentum is decreased. This results in a lower force experienced, reducing the risk of injuries.