Question

A body of mass 1kg is kept at rest.A constant force of 6N starts acting on it.Find the time taken by the body to move through a distance of 12m.

Answer 1

The time taken is t = 2s.
We have F = 6N, m = 1kg, s = 12m and u = 0m/s.
From F = ma, on substituting the given values for F and m, we get a = 6m/s².
Now, in the equation s = ut+$\frac{1}{2}$at², we substitute for s, u and a, to get t² = 4 ⇒ t = 2s (-2 is neglected since time cannot be negative).

Answer 2

F = m x a

Given, F = 6N

therefore, 6N = 1kg x a

                a = 6/1 = 6 m/s2

2as = (v)2 - (u)2

Given, u = 0 and s = 12 m

therefore, 2 x 6 x 12 = (v)2 - (0)2

                 12 x 12 = v2

                  144 = v2

                 So, v = root of 144

                             12

Now take, v = u + at

Given, u = 0 and a = 6m/s

Therefore, 12 = 0 + 6t

                  So, t = 12/6

                          =  2/1

                                                 There it took 2 seconds