Question

A body of mass 5 kg has linear momentum of 20 kgm/s.if a constant force of 5N acts on it in direction of its motion for 10s. The change in kinetic energy of the body is

Answer 1

Solution :

Given :

↪Mass = 5 kg

↪ Momentum = 50 kgm/s

↪ Force = 5 N

↪ Time = S

Solution :

P( Momentum ) = m × v

20 kg m/s = 5 kg × v

•°• v = 20 kg m/s ÷ 5 kg

v = 4 m/s

Lets find out velocity after 10 Second !

{ v = u + at }

↪v = u + (f/m)t

↪v2= v1 + ( 5/5 * 10 )

↪v2 = 4 + ( 10 )

↪v2 = 14 m/s

Now, According to the Question!

Change in kinetic of the body = mv²/2 - mv²/2

mv²/2 - mv²/2

↪m/2 ( v2² - v1² )

↪5/2 ( 14²- 4² )

↪5/2 [ ( 4 + 14 ) ( 14 - 4 ) ]

↪5/2 [ ( 18 × 10 ) ]

↪5/2 × 180

↪5 × 90

↪450 joule

Answer 2

Answer:

The change in kinetic energy of the body is 450J.

Explanation:

Given:

Mass(m)=5kg

Momentum(p)=20kgm/s

Force(F)=5N

Time(t)=10s

To find: Change in kinetic energy

Solution:
We know that,

$Momentum=Mass*Velocity$

∴Velocity=Momentum/Mass=20/5=4m/s

Therefore, u=4m/s

The velocity after 10s,

$v=u+at$

$v=u+(\frac{F}{m}t )$

v=4+10=14m/s

Change in Kinetic Energy is given by,

Δ$KE=\frac{1}{2}m(v^{2}-u^{2} )$

        =$\frac{1}{2}5(14^{2}-4^{2} )$

  ΔKE=450J

Therefore, the change in kinetic energy of the body is 450J.