What is the approximate kinetic energy of an Olympic athlete when running at maximum speed during a 100 m race?
Respuesta
A 400 J
B 4000 J
C 40 000 J
D 400 000 J
Pregunta 2
Pregunta
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.
Pregunta 3
Pregunta
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?
Respuesta
A 60 J
B 6.0 × 10^3 J
C 6.0 × 10^5 J
D 6.0 × 10^7 J
Pregunta 4
Pregunta
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?
Respuesta
A 1.7 × 10^6 J
B 3.4 × 10^6 J
C 1.7 × 10^9 J
D 3.4 × 10^9 J
Pregunta 5
Pregunta
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?
Respuesta
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.
Pregunta 6
Pregunta
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?