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Mention any two difference between the mass and weight of a body.
Difference between mass and weight of the body:
|
Mass |
Weight |
|
1. It is a scalar quantity. 2. It is the quantity of matter contained in a body.
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1. It is a vector quantity. 2. It is the force with which the earth attracts a body. |
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Define Newton, the S.I. unit of force. State its relationship with the C.G.S. unit of force.
One Newton is the amount of force required to produce an acceleration of 1 m/s2 in a body of mass 1 kg.
1 Newton = 1 kg x 1 m/s2
= 1000 g x 100 cm/s2
= 105 g cm/s2
= 10 5 dyne
That is, 1 N = 105 dyne
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.
The amount of work done will be equal to zero. This is because, work is said to be done only when there is a displacement produced. In case of a body moving in a circular path, the body comes to its original place, therefore, there is no displacement and hence work is zero.
Calculate the height through which a body of mass 0.5 kg should be lifted if the energy spent for doing so is 1.0 Joule.
Given,
Mass, m = 0.5 kg
P.E = 1.0 g
Acceleration due to gravity, g = 10 m/s2
P.E = mgh
Show that for the free fall of a body, the sum of the mechanical energy at any point in its path is constant.
Let a body of mass m fall freely under gravity from height h above ground.
Let, A B and C be the positions of body.
Let x be the distance fallen from A to B.
At position A:
K.E= 0 (body is at rest)
P.E = mgh
Therefore,
Total energy = 0 + mgh = mgh … (i)
At position B:
Let v1 be velocity of body, then u = 0
S= x
Using equation of motion, we have
V2 = u2 + 2as
V12 = 0 + 2 gx
V12 = 2 gx 
At position C:
Let velocity of body be v.
Then, u = 0 and S = h
From equation,
V2 = u2 + 2gs
V2 = 0 + 2gh
V2 = 2gh
Therefore, from equations (i), (ii) and (iii), it is clear that the sum of mechanical energy remains same at any point in the path of free fall of a body.
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