Question

give correct answer only​

Answer 1

Given :-

• Mass of a body = 30 kg
• Initial speed of a body = 20 m/s
• Final speed of a body = 15 m/s

To Find :-

• The change in kinetic energy of the body

Solution :-

• The Kinetic energy of a body is given by ,

$\\ \star \: {\boxed{\purple{\sf{KE = \dfrac{1}{2}m {v}^{2} }}}}$

First let us calculate the initial kinetic energy of the body . we have ,

• m = 30 kg
• u = 20 m/s

$\\ : \implies \sf \:KE_{i} = \dfrac{1}{2} \times 30 \times {(20)}^{2}$

$\\ : \implies \sf \: KE_{i} = 15 \times {(20)}^{2}$

$\\ : \implies \sf \: KE_{i} = 15 \times 400$

$\\ : \implies{\underline{\boxed{\red{\mathfrak{KE_{i} = 6000 \: J}}}}}$

So , The initial kinetic energy of the body is 6000 J.

Now , Let us calculate the Final kinetic energy of the body. We have ,

• m = 30 kg
• v = 15 m/s

$\\ : \implies \sf \:KE_{f} = \dfrac{1}{2} \times 30 \times {(15)}^{2}$

$\\ : \implies \sf \: KE_{f} = 15 \times {(15)}^{2}$

$\\ : \implies \sf \: KE_{f} = 15 \times 225$

$\\ : \implies{\underline{\boxed{\red{\mathfrak{KE_{f} = 3375 \: J}}}}}$

Now , Calculating the change in kinetic energy ;

• $\\ : \implies \sf \Delta \: KE = KE_{f} - KE_{i}$
• $\\ : \implies \sf \Delta \: KE = 3375 - 6000$
• $\\ : \implies{\underline{\boxed{\pink{\mathfrak {\Delta \:KE = - 2625 \: J}}}}} \: \bigstar$

Hence ,

The Change in kinetic energy of the given body is 2625 J.

Answer 2

Explanation:

Solution :-

K.E=1/2mv2

M=30kg

So, kinetic Energy =>1/2×30×20×20=6000J

When,V=15

Then,K.E=1/2×30×15×15=3375

Difference between K.E=3375-6000

=>Ans=-2225