Question

a body of mass 2 kg starts from rest and moves with uniform acceleration it acquires a velocity of 20 metre per second in 4 second the power exerted on the body in 2 second is

Answer 1

m=2 kg
u= o m/s
v= 20 m/s
t= 4 s
so, acceleration = (v-u)/t
= 20/4
= 5 m/s^2
therefore, force= 2×5=10 N
s= 1/2 at^2
= 1/2×5×16
= 40 m
so, work = force×displacement
= 10×40
= 400 j
therefore, power = work /time
= 400/2
= 200 watt

Answer 2

Question :

A body of mass 2 kg starts from rest and moves with uniform acceleration it acquires a velocity of 20 m/s in 4 seconds, the power exerted on the body in 2 second is ?

From question we have :

• IntiaI veiocity (u) = 0 m/s
• FinaI veIocity (v) = 20 m/s
• Time (t) = 4 s

At first to find acceIeration we wiII use 1st equation of motion :

⇔ v = u + at

⇒ 20 = 0 + a × 4

⇒ 20 = 4a

⇒ a = 20/4

⇒ a = 5 ms⁻²

Now finding force exerted on body :

⇔ Force = Mass × AcceIeration

⇒ Force = 2 × 5

⇒ Force = 10 N

Now we have to find distance covered by body in 4 seconds :

⇔ v² = u² + 2as

⇒ (20)² = 0² + 2 × 5 × s

⇒ 400 = 10s

⇒ s = 400/10

⇒ s = 40 m

Now finding work done by body :

⇔ Work done = Force × DispIacement

⇒ Work done = 10 × 40

⇒ Work done = 400 J

Now we wiII find power exerted :

[Here time = 2 seconds]

⇔ Power = Work done/Time

⇒ Power = 400/2

⇒ Power = 200 W

Therefore,

Power exerted on body = 200 Watts.