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Why is a jack screw provided with a long arm?
Concept: Concept of Work
If the power of a motor is 100 kW, at what speed can it raise a load of 50,000 N?
Concept: Work Done by the Force of Gravity (W = mgh)
A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare:
- The work done by them.
- The power developed by them.
Concept: Work Done by the Force of Gravity (W = mgh)
A stone of mass m is rotated in a circular path with a uniform speed by tying a strong string with the help of your hand. Answer the following questions
1) Is the stone moving with a uniform or variable speed?
2) Is the stone moving with a uniform acceleration? In which direction does the acceleration act?
3) What kind of force acts on the hand and state its direction?
Concept: Work Done by the Force of Gravity (W = mgh)
When a body is placed on a table top, it exerts a force equal to its weight downwards on the table top but does not move or fall

1) Name the force exerted by the table top
2) What is the direction of the force?
Concept: Work Done by the Force of Gravity (W = mgh)
How is work done by a force measured when the force is in the direction of displacement?
Concept: Work Done by the Force of Gravity (W = mgh)
How is work done by a force measured when the force is in an angle to the direction of displacement?
Concept: Measurement of Work
Rajan exerts a force of 150 N in pulling a cart at a constant speed of 10 m/s-1. Calculate the power exerted.
Concept: Concept of Power
Give the expression for mechanical advantage of an inclined plane in terms of the length of an inclined plane.
Concept: Work Done by the Force of Gravity (W = mgh)
Name a common device where a gear train is used
Concept: Concept of Work
Draw a simplified diagram of a lemon crusher, indicting of load and effort
Concept: Work Done by the Force of Gravity (W = mgh)
Explain briefly why the work done by a fielder when he takes a catch in a cricket match is negative.
Concept: Concept of Work
When does a force do work?
Concept: Work Done by the Force of Gravity (W = mgh)
What is the work done by the moon when it revolves around the earth?
Concept: Concept of Work
Calculate the change in the Kinetic energy of a moving body if its velocity is reduced to 1/3rd of the initial velocity.
Concept: Forms of Energy > Solar Energy
State the energy change in the following device while in use:
A loudspeaker
Concept: Forms of Energy > Solar Energy
State the energy change in the following device while in use:
A glowing electric bulb.
Concept: Forms of Energy > Solar Energy
What is nuclear energy?
Concept: Forms of Energy > Solar Energy
Name the process used for producing electricity using nuclear energy.
Concept: Forms of Energy > Solar Energy
State one important advantage and disadvantage each of using nuclear energy for producing electricity.
Concept: Forms of Energy > Solar Energy
