Question

if a net force of 7N was constantly applied on 400g obj at rest ,how long will it take to raise it's velocity to 80m/s​

Answer 1

Given

F = 7N

m = 400g = 0.4kg

v = 80 m/s

u = 0

To Find

Time (t)

Solution

W.k.t,

$\blue{\boxed{\pink{F = ma}}}$

$\mathsf{a = \dfrac{F}{m}}$

$\mathsf{a = \dfrac{7}{0.4}}$

$\mathsf{a = 17.5 m{s}^{-2}}$

Now

From the eq. of motion

$\blue{\boxed{\pink{v = u + at}}}$

$\mathsf{80 = 0 + (17.5)t}$

$\mathsf{80 = 17.5t}$

$\mathsf{t = \dfrac{80}{17.5}}$

$\mathsf{t = 4.57 sec}$

$\mathsf{t ≈ 5 sec}$