6 marks*A student of weight 600 N is standing on weighing scales in a lift. The scales are calibrated to give readings in newtons.
The lift moves upwards at constant velocity, then decelerates to rest. As the lift moves, the student looks at the readings on the scales.
Explain the readings on the scales.
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2 marksAn aluminium sphere collides head-on with a stationary steel sphere. The two spheres move off separately after the collision.
State the principle of conservation of momentum.
3 marksThe aluminium sphere has an initial velocity of 10.0 m s–1. Immediately after the collision the velocity of the steel sphere is 5.0 m s–1.
Calculate the velocity v of the aluminium sphere immediately after the collision.
mass of aluminium sphere = 2.7 kg
mass of steel sphere = 7.9 kg
v = .............................................
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2 marksA 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.
5 marks
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 (3)
Velocity of asteroids = .................................
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2 marksA 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 .
2 marksCalculate the velocity of the second carriage before the collision.
Velocity of second carriage = ..........................
2 marksCalculate the change in total kinetic energy during the collision.
Change in total kinetic energy = ............................
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6 marks*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.
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4 marksA 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.
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