Conservation of momentum in collisions and explosions

Question 1

A 2 kg toy cannon at rest fires a 0.05 kg ball forwards at 500 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s

Question 2

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 3

A 3 kg trolley moving at 3 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 4

A 2 kg toy cannon at rest fires a 0.02 kg ball forwards at 400 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s

Question 5

Why does a rocket in space accelerate forwards when it pushes exhaust gases backwards?

• A. Gravity pushes it
• B. Momentum is not conserved in space
• C. The gases gain backward momentum, so the rocket gains equal forward momentum
• D. It pushes against the air

Question 6

A 2 kg trolley moving at 3 m/s hits a stationary 4 kg trolley. They stick together. What is their velocity just after the collision, in m/s? (Give 2 decimal places.)

Answer m/s

Question 7

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 8

Two ice skaters at rest push apart. Skater A (40 kg) moves off at 3 m/s. What is the total momentum of the two skaters afterwards?

• A. 40 kg m/s
• B. 120 kg m/s
• C. 240 kg m/s
• D. 0 kg m/s

Question 9

A 1000 kg car moving at 10 m/s hits a stationary 2000 kg car. They lock together. What is their velocity just after the collision, in m/s? (Give 2 decimal places.)

Answer m/s

Question 10

A 2 kg toy cannon at rest fires a 0.05 kg ball forwards at 200 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s

Question 11

Why does a rocket in space accelerate forwards when it pushes exhaust gases backwards?

• A. It pushes against the air
• B. The gases gain backward momentum, so the rocket gains equal forward momentum
• C. Momentum is not conserved in space
• D. Gravity pushes it

Question 12

A 2 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 4 kg toy cannon at rest fires a 0.02 kg ball forwards at 500 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s

Question 14

In which situation is momentum conserved?

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

Question 15

A 2000 kg car moving at 3 m/s hits a stationary 800 kg car. They lock together. What is their velocity just after the collision, in m/s? (Give 2 decimal places.)

Answer m/s

Question 16

A 4 kg toy cannon at rest fires a 0.02 kg ball forwards at 400 m/s. What is the recoil speed of the cannon, in m/s?

Answer m/s