Question

A stone of mass 1 kg thrown with an initial velocity of 20 m/s over a frozen lake comes to rest after 10 s . Find the magnitude of the force.

a)2 N
b)1 N
c)-2 kgm/s2
d)-1 kgm/s2​

Answer 1

Answer:

-4N

Explanation:

Given:

The initial velocity of the stone, u= 20 m/s

The final velocity of the stone, v= 0

Distance covered by the stone, s= 50 m

Find out:

The force of friction between the stone and the ice

Solution

We know the third equation of motion

v² = u² + 2as

Substituting the known values in the above equation we get,

0² = (20)² + 2(a)(50)

-400 = 100a

a = -400/100 = -4m/s² (retardation)

We know that

F = m×a

Substituting above obtained value of a = -4 in F = m x a we get,

F = 1 × (-4) = -4N