Question

WORKSHEET-1
SUBJECT- SCIENCE
TOPIC-FORCE & LAWS OF MOTION
A constant regarding force of 50 N is applied to a body of mass 20 kg, moving with a speed of 15
m/s. How long does the body take to stop?
(A 5s
(B) 6 s
c 8s
d 10s​

Answer 1

Given that,

Force F=50N

Mass m=20kg

Initial velocity u=15m/s

Now, from newton’s second law

F=ma

50=20×a

a=2.5m/s2

Now from equation of motion

v=u+at

0=15+(−2.5)t

t=15/2.5

t=6s

Hence, the body will be stop in 6 sec.

B. Given that,

Mass of the body,m=3 kg

Initial speed of the body u=2 m/s

Final speed of the body v=3.5 m/s

Time, t=25 sec

Now, for acceleration

Use the equation of motion

v=u+at

a= (v−u)/t

a=

3.5−2/25

a= 1.5/2.5

a=0.06 m/s2

Now, for the force

Use the newton’s second law

F=ma

F=3×0.06

F=0.18 N

The magnitude of the force is 0.18 N.