i) Which of the following remains constant in uniform circular motion: Speed or velocity or both?
ii) Name the force required for uniform circular motion. State its direction.
i) Speed remains constant.
ii) Centripetal force, directed towards the centre of the circle.
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2.
A ball is placed on a compressed spring. When the spring is released, the ball is observed to fly away.
i) What form of energy does the compressed spring possess?
ii) Why does the ball fly away?
i) Potential energy
ii) Since
P.E is converted into Kinetic energy which transferred to the ball and makes the ball fly away.
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3.
A boy of mass 30 kg is sitting at a distance of 2 m from the middle of as ea-saw. Where should a boy of mass 40 kg sit so as to balance the sea-saw?
Let the boy of mass 40 kg is sitting at a distance of x m from the middle of the see-saw on other side of the boy of mass 30
kg to balance the see-saw.
Now, using principle of moments,
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4.
State the class of levers and the relative positions of load (L), effort (E) and fulcrum (F) in each of the following cases:
1. A bottle opener 2. Sugar tongs
1. A
bottle opener – Class II lever
Load between Fulcrum and Effort
2. Sugar Tongs – Class III lever
Effort between Fulcrum and Load
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5.Why is less effort needed to lift a load over an inclined plane as compared to lifting the load directly?
For an inclined plane, mechanical advantage = L/E =
1 (since l > h).
Therefore,
Effort, E < Load L
Hence, less effort is required because mechanical advantage increases.
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6.
i) What are non-contact force?
ii) How does the distance of separation between two bodies affect the magnitude of the non-contact force between
them?
i) The forces which are applied from a distance, without actually touching the body is called non-contact forces.
ii) As the distance of separation increases, the magnitude of non-contact forces decreases.
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7.
i) Define 1 kgf
ii) How is it related to the S.I. unit of force?
i) 1 kgf is the force with which the earth
pulls an object of mass 1 kg towards itself.
ii) 1 kgf = 9.8 N
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8.
A body of mass 0.2 kg falls from a height of 10 m to a height of 6 m above the ground. Find the loss in Potential energy taking place in the body.
Given,
mass, m = 0.2 kg
g = 10 m/s2
h1 = 10 m, h2 = 6 m
Loss in Potential Energy= mg (h1
- h2)
= 0.2 × 10 × (10-6)
= 0.2 × 10× 4
= 8 J
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9.
i) State the energy conversion taking place in a solar cell?
ii) Give one disadvantage of using a solar cell
i) In a solar cell the light energy changes to electrical energy.
ii) 1. Solar cell is not a constant source of energy.
2. The efficiency of conversion of light energy into electrical energy is very low.
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10.
i) What is meant by the term ‘moment of force’?
ii) If the moment of force is assigned a negative sign then will the turning tendency of the force be clockwise or anti-clockwise?
i) Turning effect of force acting on a body about an axis is called moment of force. It is equal to the product of magnitude of force and the perpendicular distance of the line of action of force from the axis of rotation.
ii) Clockwise.
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How do inclined planes reduce effort?
Inclined planes make it easier to move objects to a higher elevation. The sloping surface of the inclined plane supports part of the weight of the object as it moves up the slope. As a result, it takes less force to move the object uphill.
Why is less effort needed to lift a load over an inclined plane?
Hence we can say that less effort is required to lift a load over an individual plane because mechanical advantage increases.
How could I reduce the effort force needed to lift the load?
By increasing the distance from the fulcrum to the point where the effort force is applied, or by decreasing the distance the weight is from the fulcrum. 1. 2. By increasing the distance the effort force moves relative to the distance the weight moves, a lever can reduce the effort force needed.
How does an inclined plane affect the effort needed to move a load vertically?
Pushing the load up the ramp means that it moves along a distance that is double the vertical height. The payoff is that the effort required is only half that needed to lift the load vertically the same distance. The general rule is that a less steep slope means that the object moves further, but the effort is less.
