Force and Laws of Motion — Question 5

Given,

Distance (s) = 400 m

Time (t) = 20 sec

Initial velocity (u) = 0

According to the second equation of motion,

S = ut + $\dfrac{1}{2}$at²

Substituting we get,

400 = 0 + $\dfrac{1}{2}$ x a x 20 x 20

a = $\dfrac{400 \times 2}{20 \times 20}$ = 2 ms^-2

∴ acceleration of the car = 2 ms^-2.

Now, mass = 7 tonnes

Converting tonne into kg

1 tonne = 1000 kg

∴ 7 tonnes = 7000 kg

Force = mass x acceleration

F = 7000 x 2 = 14000 N

Hence, Force acting = 14000 N