Question

how long will it take a force of 10N to stop a mass of 2.5kg which is moving at 20m/s

Answer 1

F=ma.

10=2.5 a

a=10/2.5

a=4m/s^2

now,

v=0 , u=20 , a=4m/s^2

v=u+at

0=20+4t

t=-20/4

therefore t= 5sec.

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 second.