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,
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.
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
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
A bottle opener – Class II lever
Load between Fulcrum and Effort
Sugar Tongs – Class III lever
Effort between Fulcrum and Load
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.
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).
Effort, E < Load L
Hence, less effort is required because mechanical advantage increases.
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.
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.
i) Define 1 kgfii) 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
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.
1. Solar cell is not a constant source of energy.
2. The efficiency of conversion of light energy into electrical energy is very low.
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.