Question

If a body of mass 5 kg is moving along a straight line with velocity 10 m/s and acceleration 20 m/s2. Find its kinetic energy after 10 s

Answer 1

M=5kg

P(momentum)=10kg-m/s

F=0.2N

Time=10sec

P=mv= 5×v=10= 2m/s

V(initial) =2m/s

F=ma= 5×a =0.2=0.04m/s^2

Finding final velocity

V=u+at

V= 2+ 0.04×10

V=2.4 m/s

Kinetic energy =1/2 mv^2

Change in kinetic energy=

1/2mVf^2 － 1/2mVi^2

1/2×5×2.4^2 － 1/2×5×2^2= 4.4J

Answer 2

Kinetic energy, K = 110250 J

Explanation:

It is given that,

Mass of the body, m = 5 kg

Initial speed of the body, u = 10 m/s

Acceleration, $a=20\ m/s^2$

Time, t = 10 s

Let v is the final speed of the body. We can calculate it using the first equation of motion as :

$v=u+at$

$v=10+20\times 10$

v = 210 m/s

Let K is the kinetic energy of the body. The expression for the kinetic energy is given by :

$K=\dfrac{1}{2}mv^2$

$K=\dfrac{1}{2}\times 5\ kg\times (210\ m/s)^2$

K = 110250 J

So, the kinetic energy of the body after 10 s is 110250 Joules.

Learn more :

Topic : Kinetic energy

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