Short Answer TypeDefine Newton, the S.I. unit of force. State its relationship with the C.G.S. unit of force.
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.
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.
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.
A uniform metre scale is kept in equilibrium when supported to the 60 cm mark and a mass M is suspended from the 90 cm mark as shown in the figure. State with reasons, whether the weight of the scale is greater than, less than or equal to the weight of mass M. 
Name the type of single pulley that can act as a force multiplier. Draw a labelled diagram of the above named pulley.
A pulley system has a velocity ratio of 4 and an efficiency of 90%. Clculate:
i) the mechanical advantage of the system.
ii) the effort required to raise a load of 300 N by the system.Give one use each of the electromagnetic radiations given below:
i) Microwaves
ii) Ultraviolet radiations
iii) Infrared radiation.
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