Question

A truck starts from rest and rolls down a hill with a constant acceleration . It travels a distance of 400 m in 20 seconds . Find its acceleration. Find the force acting on it if it's mass is 7 tonnes.

Answer 1

Answer: 7000N

Explanation:s=400m , t=20sec. , start from rest=>u=0

        s=ut-1/2at^2

  so 400=0*20-a*(20^2)

    a=1 m/s^2

Force=ma    m=7000kg ,a=1m/s^2

  =7000*1

  =7000 Newton

Answer 2

$\bf{\underline{\underline{Answer:}}}$

∴$\:\bf 14000\: N$

$\bf{\underline {Given:}}$

$⟹Initial\: velocity \:of \:truck\:, u=0$

(since, truck starts from rest)

$⟹ Distance\: travelled, \:s = 400\: m$

$⟹Time, \: t = 20\: s$

$\bf{\underline {To\:Find:}}$

$⟹Acceleration, a=\:?$

$\bf{\underline{\underline{Step\: by\: step \:explanation:}}}$

We know that,

$⟹s=ut+\dfrac{1}{2}at^2$

$⟹400 =0×20+\dfrac{1}{2}×a×{(20)}^{2}$

$⟹400 =0+\dfrac{1}{2}×a×400$

$a=\dfrac{400}{200}=2\:m\:s^{-2}$

Force acting upon truck,

Mass of truck = 7 tonnes = 7 × 1000 kg = 7000 kg

We know that,

Force, $F = m × a$

Therefore, $F=7000×2\:kg\:m\:s^{-2}$

Or$\:\:\:\:\:\:\:\:\:\:F = 14000 \:Newton$

Thus, acceleration of the truck is $\bf 2 \:m\:s^{-2}$ and force acting upon truck in the given condition is 14000 N.