Question

A body with mass 5 kg is acted upon by a force F=(-3i+4j)N.If its initial velocity at t= 0 is u= (6i-12j)m/s,the time at which it will just have a velocity along Y-axis?

Answer 1

Answer:

Explanation:

To find the time in which the velocity of the body will be entirely along y-axis,  consider the final x-component of velocity to be zero.

For the motion along x-axis,

F = -3 N, therefore, a=-3/5 m/s2

u = 6 m/s

v = 0 m/s

Applying the eqn,

v = u + at

0 = 6 - 3t/5

t = 10 s

Answer 2

Given :-

Mass of the body = 5 Kg

Force = F = (-3î + 4j) N.

Initial velocity = u = (6î - 12j) ms-¹.

Here, we need to find Velocity in y-direction only it means we must have velocity in x-direction is zero.

F = ma

a = F/m

a = (-3î/5 + 4j/5) ms-²

${a}_{x}$= (-3/5)î

${u}_{x}$= 6î

Using First equation of Motion,

${v}_{x} = {u}_{x}+{a}_{x}t$

0 = 6 - 3/5t

3/5 t = 6

t = 10 s

Hence,

The time when body will have velocity in x-direction as Zero = 10 s it means body will have velocity along y-direction only.