11th grade forces and motion

Question 1

A 80 kg passenger moving at 12 m/s is brought to rest in 0.1 s by a seat belt and airbag. What is the average force on the passenger, in N?

Answer N

Question 2

A car travelling at 30 m/s brakes with a deceleration of 10 m/s². What is its braking distance, in m? (Give 1 decimal place.)

Answer m

Question 3

A 3 kg trolley moving at 2 m/s hits a stationary 2 kg trolley. They stick together. What is their velocity just after the collision, in m/s? (Give 2 decimal places.)

Answer m/s

Question 4

A helmet increases the time for a head to stop in a fall from 0.02 s to 0.1 s. The change in momentum is the same. By what factor is the average force reduced?

Answer 

Question 5

A 4 kg toy cannon at rest fires a 0.01 kg ball forwards at 300 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s

Question 6

In a car crash test, momentum is conserved but kinetic energy is not. Where does the kinetic energy go?

• A. into extra momentum
• B. into deforming the cars, heating them and sound
• C. it is destroyed
• D. into the cars' nuclear store

Question 7

Why do cricket or baseball fielders pull their hands back as they catch a fast ball?

• A. It increases the time to stop the ball, reducing the force on their hands
• B. It makes the ball lighter
• C. It increases the ball's speed
• D. It changes the ball's momentum to zero instantly

Question 8

An object starts at 4 m/s and accelerates uniformly at 3 m/s² over 20 m. What is its final velocity, in m/s? (Give 1 decimal place.)

Answer m/s

Question 9

A train speeds up from 5 m/s to 15 m/s over 25 m. What is its acceleration, in m/s²? (Give 2 decimal places.)

Answer m/s²

Question 10

A 80 kg passenger moving at 15 m/s is brought to rest in 0.05 s by a seat belt and airbag. What is the average force on the passenger, in N?

Answer N

Question 11

A car travelling at 20 m/s brakes with a deceleration of 10 m/s². What is its braking distance, in m? (Give 1 decimal place.)

Answer m

Question 12

A 1 kg trolley moving at 6 m/s hits a stationary 1 kg trolley. They stick together. What is their velocity just after the collision, in m/s? (Give 2 decimal places.)

Answer m/s

Question 13

A helmet increases the time for a head to stop in a fall from 0.02 s to 0.08 s. The change in momentum is the same. By what factor is the average force reduced?

Answer 

Question 14

A 4 kg toy cannon at rest fires a 0.05 kg ball forwards at 400 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s

Question 15

In which situation is momentum conserved?

• A. in a closed system with no external forces
• B. only when objects are stationary
• C. never
• D. only in elastic collisions

Question 16

Why do cyclists' helmets contain crushable foam?

• A. Crushing foam increases the time the head takes to stop
• B. Foam reduces air resistance
• C. Foam is heavier than plastic
• D. Foam makes the helmet bounce