Question

A body with mass 5 kg is acted upon by a force F = `( –3hati + 4hatj)` N. If its initial velocity at t = 0 is v = `(6hati - 12hatj)` ms^–1, the time at which it will just have a velocity along the y-axis is ______.

Options

• never

• 10 s

• 2 s

• 15 s

Answer 1

A body with mass 5 kg is acted upon by a force F = `( –3hati + 4hatj)` N. If its initial velocity at t = 0 is v = `(6hati - 12hatj)` ms^–1, the time at which it will just have a velocity along the y-axis is 10 s.

Explanation:

Since `veca = (vecF)/m` hence, we have `veca = 1/5 (- 3hati + 4hatj) N`

Now, since the x-component of the final velocity is zero,

Hence, `v_x = u_x + a_xt`

0 = `6hati + (- 3hati)/5 t`

That gives us t = 10 s.