(a) A body of mass 5.5 kg is dropped from the 2nd floor of a building which is at a height of 15 m. What is the force acting on it during its fall? (g = 10 ms^-2)

(b) What are isobars ?

(c) How many pulleys are there in a movable block and tackle system with velocity ratio 5 ?

(a) Given,

mass (m) = 5.5 kg

height (h) = 15 m

force acting on it during its fall = ?

Force acting on the body during its fall = weight of the body.

And F = mg

Substituting we get,

F = 5.5 x 10 = 55 N

Hence, Force acting on the body during its fall = 55 N

(b) The atoms of different elements which have the same mass number A but different atomic number Z are called isobars.

Example — $^{23}${11}\text{Na} and $^{23}{12}\text{Mg}$ are isobars.

(c) The number of pulleys required in the movable block of a block and a tackle system with velocity ratio 5 will be 5.