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State the amount of work done by an object when it moves in a circular path for one complete rotation. Give a reason to justify your answer.
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Why is less effort needed to lift a load over an inclined plane as compared to lifting the load directly?
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In what way does an ‘Ideal machine’ differ from a ‘Practical machine’?
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State larger units of power.
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What do you understand by the term energy? Is energy a scalar or vector? How is the energy possessed by a body measured?
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A man climbs a slope and another walks same distance on level road. Which of the two expends more energy and why?
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Name the material commonly used for the manufacturing of solar cells.
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Name two places in India where electricity is generated from nuclear power plants.
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What should be the characteristic of a source of energy?
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Explain, why submarines are able to dive underwater as well as a sail on the surface of the water?
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Give two examples each of contact and non-contact forces.
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What is the difference between renewable and non-renewable resources?
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What are the advantages and disadvantages of using solar cells for producing electricity?
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A block of mass 30 kg is pulled up a slope, as shown in diagram with a constant speed, by applying a force of 200 N parallel to slope.
A and B are initial and final positions of block.

(i) Calculate the work done by force in moving the block from A to B.
(ii) Calculate P.E. gained by block. [g=10ms-2]
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(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?
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A truck driver can load oil drums into the back of the truck by pushing them up a sloping plank, or by lifting them directly. Each drum has a mass of 80 kg, the plank is 3 m long, and the back of the truck is 0.8 m above the ground.

(i) How much force would be needed to lift a drum into the truck directly/without using the plank? (Take g = 10 m/s2)
(ii) How much energy would be required in lifting the drum into the truck without the plank?
(iii) If the force needed to push the drum up the plank is 300 N, why is this less than the answer to part (i)?
(iv) When the truck is loaded, the driver drives off. List the major energy changes that take place in moving the truck.
(v) The driver has to stop at the factory gates. What happens to the kinetic energy of the truck?
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A man can open a nut by applying a force of 150 N by using a lever handle of length 0.4 m. What should be the length of the handle if he is able to open it by applying a force of 60 N?
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Calculate the work done when:
A 5 kg weight is lifted 10 m vertically. (g = 9.8 m/s2)
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A force is applied on a body of mass 20 kg moving with a velocity of 40 ms−1. The body attains a velocity of 50 ms−1 in 2 seconds. Calculate the work done by the body.
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