Forces & Momentum (Edexcel International A Level Physics)

A slow moving asteroid A was hit by a faster asteroid B. Asteroid B was absorbed by asteroid A as shown.

State the principle of conservation of linear momentum.

Before the collision, asteroid A had a velocity of 2.19 × 10³ m s⁻¹ and a momentum of 1.80 × 10¹⁷ kg m s⁻¹.

i) Show that the mass of asteroid A was about 8.2 × 10¹³ kg.                      (2)

  ii) Calculate the velocity of the asteroids after the collision.

mass of asteroid B = 5.90 × 10¹² kg

velocity of asteroid B before the collision = 15.0 × 10³ m s⁻¹               

Velocity of asteroids = .................................(3)

A railway carriage of mass 7.15 × 10⁴ kg moving at 4.50 m s⁻¹ collides with a second railway carriage of mass 5.35 × 10⁴ kg moving in the same direction.

The carriages join together. Immediately after the collision they move at a speed of 3.62 m s⁻¹ .

Show that the total momentum of the carriages immediately after the collision was approximately 4.5 × 10⁵ kg m s⁻¹ .

Calculate the velocity of the second carriage before the collision.

Velocity of second carriage = ..........................

Calculate the change in total kinetic energy during the collision.

Change in total kinetic energy = ............................

*A large spacecraft is made up of several ‘stages’. Each stage consists of a rocket motor and a fuel tank. Once a stage has used all its fuel, the rocket motor in that stage shuts down. The stage then disconnects from the spacecraft and falls back to Earth.

As the rocket is rising due to the upward force of the first stage, an astronaut feels himself pushed further and further back, compressing the back of his seat.

When the first stage shuts down, the astronaut is suddenly projected forwards by the seat. The astronaut is held in place by a safety strap.

Explain the effects experienced by the astronaut. You may assume that the force provided by the first stage rocket motor is constant until the moment it shuts down.

A helicopter can hover in a fixed position as shown.

The helicopter blades move air vertically downwards.

Explain how this enables the helicopter to maintain a constant height above the ground.