Question

Starting from rest a car acquires a velocity of 18 km h¹ in 20 s. If the mass of car is 100 kg, find the force exerted by the engine.​

Answer 1

Given :

u = 0.

V = 18 km/hr = 5 m/s

t = 20 s

m = 100 kg

F = ?

solution:

By the first kinematical equation we have,

v = u + at

a = v-u/t

a = 5-0/20

a = 1/4

Now we know,

F = m a

F = 100×1/4

F = 25 N is the required force exerted by the engine

Answer 2

Answer:

u =0 m/s (body starts from rest)

v = 180 m/s

t =0.05h=180s

Using first equation of motion,

v=u+at

a =

t

v−u

=

180

180−0

=1

s

2

m