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Can there be displacement of an object in the absence of any force acting on it? Think. Discuss this question with your friends and teacher.
What is the work done by the moon when it revolves around the earth?
When is work said to be done by a force?
State two disadvantages of producing hydroelectricity.
State the energy transformation on the following:
Electricity is obtained from solar energy.
What do you mean by degradation of energy?
A person of mass 50 kg climbs a tower of height 72 metres. Calculate the work done. (g = 9.8 m s−2).
How much work is done by the gravitational force of earth acting on a satellite moving around it in a circular path? Give reason for your answer.
A boy does work when he pushes against a brick wall. (yes/no).
What is the work done against gravity when a body is moved horizontally along a frictionless surface?
Write an expression for work done by a force depends?
A boy of mass m climbs up a staircase of vertical height h.
- What is the work done by the boy against the force of gravity?
- What would have been the work done if he uses a lift in climbing the same vertical height?
In the following case write yes, if the work is being done and no if no work is being done.
A coolie standing with a heavy load on his head
A man climbs a slope and another walks same distance on level road. Which of the two expends more energy and why?
(i) A 200g ball is thrown vertically upward with an initial velocity of 30 ms-1. Draw a velocity-time graph for the motion of ball.
(ii) How long will the ball take to reach the highest point?
(iii) What will be the kinetic energy of ball, when it returns to the starting point, neglecting the air resistance?
(iv) What will be the potential energy of ball at highest point?
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A wind-mill is lifting water from a well.
Force acting on a particle moving in a straight line varies with the velocity of the particle v as F = `K/v`, where K is a constant. The work done by this force in time t is
