1. Edexcel Homework for Topic 10
(Rollercoasters and relativity)
Questions 1: Work
1. Three people do 2,000 J of work; what distance do they move if:
(a) person A exerts a force of 200 N?
(b) person B pushes with a force of 50 N?
(c) person C uses a force of 0.8 N?
2. How much work is done if:
(a) a man weighs 750 N and uses the stairs to climb 50 m
(b) a woman lifts a 400 N rucksack onto her back, a height of 1.2 m
(c) a pebble of weight 0.2 N is thrown 5 m into the air?
3. A lorry takes 30 m to slow down and stop. If its brakes exert a force of
20,000 N, then:
(a) how much work do the brakes do
(b) what is the maximum amount of heat generated
(c) how much kinetic energy did the lorry have?
Questions 2: Power
1. Calculate the power of an engine that can:
(a) do 1,200 joules of work in 4 seconds
(b) lift a 200 N weight through 30 metres in 12 seconds
(c) drive a car 500 metres in 25 seconds against air resistance of 3,000 N.
2. A machine has a power output of 500 kilowatts.
(a) How quickly will it do 4,000 kJ of work?
(b) How much work can it do in one minute?
Questions 3: Kinetic Energy
1. Explain, using the words kinetic energy, work, thermal energy, why a car
travelling at 10 m/s (22.5 miles per hour) can brake in a quarter of the distance
needed by a car travelling at 20 m/s (45 miles per hour).
2. Calculate the kinetic energy of:
(a) a person of mass 70 kg running at 8 m/s
(b) a rabbit of mass 4 kg hopping at 15 m/s
(c) a ball bearing of mass 0.016 kg rolling at 3 m/s.
Questions 4: Potential Energy
1. Explain, using the words energy, work, potential, kinetic and velocity why a
roller coaster gets faster as it goes down a slope.