Question

The taken by a force of 10N to stop a mass of 2.5kg which is moving at 20m/s is –
a. 0.5 s, b. 5 s, c. 50 s, d. 0.05 s.

Answer 1

Hi there !

Force = F = 10 N

Mass = m = 2.5 kg

Initial velocity = u = 20 m/s

Final velocity = v = 0 [ coming to rest ]

F = ma

a = F /m

= 10/2.5

= 4 m/s^2

Equation of motion :-

v = u + at

0 = 20 + 4t

4t = 20

t = 20/4

t = 5 sec

Answer 2

Answer:

force applied(F)= -10N (since the force is acting in the opp. direction of motion or opposing the motion)

mass of body(m)=2.5kg

initial velocity of body(u)=20m/s

final velocity of body(v)=0m/s

According to newton's seond law of motion

F=ma

-10=2.5*a

-10/2.5=v-u/t (since a=v-u/t)

-4t=0-20

t=-20/-4

t=5 sec.

5 seconds is correct answer.