Question

an object when falls from rest possess 400J of kinetic energy at the end of 2sec.calculate the mass of the object

Answer 1

Given:
Kinetic energy=K.E=400J
time=t=2sec
u=0m/s
mass=m=?
Let us find out Velocity at the end of 2sec:
From first equation of motion:
V=u+gt
V=0+10x 2 [∵g=10m/s²]
=20 m/s
K.E=mV²/2
m=2XK.E/V²
⇒2x400/20x20
⇒2kg
∴ Mass of the object is 2kg

Answer 2

Answer:

Given:

Kinetic energy=K.E=400J

time=t=2sec

u=0m/s

mass=m=?

Let us find out Velocity at the end of 2sec:

From first equation of motion:

V=u+gt

V=0+10x 2 [∵g=10m/s²]

=20 m/s

K.E=mV²/2

m=2XK.E/V²

⇒2x400/20x20

⇒2kg

∴ Mass of the object is 2kg