Physics
Motion, forces and energy — Topic 1
- 1.
A cyclist increases speed uniformly from 4.0 m/s to 10.0 m/s in 3.0 s. Calculate the acceleration and the distance travelled during this time.
[4 marks] - 2.
A motor lifts a 240 N load vertically through 5.0 m in 8.0 s. Calculate the work done and the useful power output.
[4 marks] - 3.
A resultant force of 15 N acts on a 3.0 kg trolley. Calculate its acceleration.
[2 marks] - 4.
A 0.50 kg ball moving at 8.0 m/s collides with a stationary 1.5 kg ball and they stick together. Calculate their common velocity after the collision, using conservation of momentum.
[4 marks] - 5.
A stone of mass 0.20 kg is dropped from a height of 5.0 m. Calculate its speed just before hitting the ground, using energy conservation. Use g = 10 m/s².
[4 marks] - 6.
State Newton's third law of motion, and use it to explain the forces acting when a swimmer pushes against the water to move forward.
[3 marks] · no calculator - 7.
A spring has an unstretched length of 12 cm. When a 4.0 N force is applied, it stretches to 16 cm. Calculate the spring constant.
[3 marks] - 8.
Explain, in terms of momentum, why a car's crumple zone reduces injury to passengers during a collision.
[3 marks] · no calculator - 9.
A crane lifts a 500 kg load through a vertical height of 12 m in 20 s. Calculate the useful power developed by the crane. Use g = 10 m/s².
[4 marks] - 10.
A car of mass 1200 kg travelling at 20 m/s brakes and comes to rest, decelerating uniformly over 40 m. Calculate the braking force, using the work-energy relationship.
[4 marks] - 11.
A block of aluminium has a mass of 540 g and a volume of 200 cm³. Calculate its density.
[3 marks] - 12.
A brick of weight 24 N rests on the ground, with a base area of 0.03 m². Calculate the pressure it exerts on the ground.
[3 marks] - 13.
A uniform beam is pivoted at its centre. A weight of 20 N hangs 1.5 m to the left of the pivot. Calculate the distance from the pivot at which a 30 N weight must be hung on the right for the beam to balance.
[4 marks] - 14.
A distance-time graph for a cyclist shows: a straight line rising steadily from 0-5 s, a horizontal line from 5-10 s, then a straight line rising more steeply than the first section from 10-15 s. Describe the cyclist's motion in each of the three sections.
[3 marks] · no calculator - 15.
The speed-time graph for a car shows its speed increasing uniformly from 0 to 20 m/s in 8.0 s, then remaining constant at 20 m/s for a further 12 s. Calculate (a) the acceleration during the first 8.0 s, and (b) the total distance travelled in the 20 s.
[5 marks] - 16.
A skydiver jumps from an aircraft and falls, eventually reaching a constant maximum speed called terminal velocity, before opening their parachute. Explain, in terms of forces, why the skydiver's speed becomes constant.
[3 marks] · no calculator - 17.
State the difference between a scalar quantity and a vector quantity, giving one example of each.
[2 marks] · no calculator - 18.
A 2.0 kg trolley moving at 3.0 m/s to the right collides with a wall and rebounds at 1.0 m/s to the left. Taking the rightward direction as positive, calculate the change in momentum of the trolley.
[4 marks] - 19.
An electric motor is supplied with 500 J of electrical energy and produces 350 J of useful kinetic energy output, the rest being wasted as heat. Calculate the efficiency of the motor.
[3 marks] - 20.
The gravitational field strength on the Moon is 1.6 N/kg, compared with 10 N/kg on Earth. An astronaut has a mass of 80 kg. Calculate the astronaut's weight on the Moon, and state what happens to the astronaut's mass.
[3 marks] - 21.
A spring with spring constant 150 N/m is compressed by 0.20 m. Calculate the elastic potential energy stored in the spring.
[3 marks] - 22.
A ball is whirled at a constant speed in a horizontal circle at the end of a string. State the direction of the resultant force acting on the ball, and explain why a resultant force is needed even though the ball's speed is not changing.
[3 marks] · no calculator - 23.
A car travels along a straight, level road at a constant velocity of 15 m/s. State what can be deduced about the resultant force acting on the car, and explain your reasoning.
[2 marks] · no calculator - 24.
A skier of mass 60 kg starts from rest and slides down a slope, descending a vertical height of 20 m. At the bottom, the skier's speed is 18 m/s. Calculate the kinetic energy gained and the energy lost to friction and air resistance. Use g = 10 m/s².
[5 marks] - 25.
A 900 kg car decelerates uniformly from 20 m/s to rest in 4.0 s during an emergency stop. Calculate the average braking force acting on the car, using the impulse-momentum relationship.
[4 marks]