What is the approximate kinetic energy of an Olympic athlete when running at maximum speed during a 100 m race?
A 400 J
B 4000 J
C 40 000 J
D 400 000 J
Two identical, perfectly elastic spheres have the same mass m. They travel towards each other with the same speed v along a horizontal frictionless surface.
Which statement about the sum of the kinetic energies of the spheres is correct?
A The sum of their kinetic energies before impact is zero.
B The sum of their kinetic energies before impact is 1/2 mv^2.
C The sum of their kinetic energies after impact is zero.
D The sum of their kinetic energies after impact is mv^2.
A piston in a gas supply pump has an area of 500 cm2 and it moves a distance of 30 cm during one stroke. The pump moves the gas against a fixed pressure of 4000 Pa.
How much work is done by the piston during one stroke?
A 60 J
B 6.0 × 10^3 J
C 6.0 × 10^5 J
D 6.0 × 10^7 J
A railway engine accelerates a train of total mass 1200 tonnes (1 tonne = 1000 kg) from rest to a speed of 75 m s^–1.
How much useful work must be done on the train to reach this speed?
A 1.7 × 10^6 J
B 3.4 × 10^6 J
C 1.7 × 10^9 J
D 3.4 × 10^9 J
The diagram shows a hydroelectric power station. The reservoir is linked to the turbines by a pipe of uniform cross-sectional area. Water flows from the reservoir, through the pipe and through the turbines at a constant rate.
Which statement about the change of energy of the water as it moves from X to Y is correct?
A It gains both gravitational potential energy and kinetic energy.
B It loses gravitational potential energy and gains elastic potential energy.
C It loses gravitational potential energy and gains kinetic energy.
D It loses both elastic potential energy and gravitational potential energy.
A concrete cube of side 0.60 m and uniform density 2.0 × 10^3 kg.m^–3 is lifted 5.0 m vertically by a crane.
What is the change in potential energy of the cube?
A 2.2 kJ
B 21 kJ
C 59 kJ
D 450 kJ
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