Question

a body of mass 12 KG moves with a speed of 20 metre per second what is its kinetic energy​

Answer 1

Relationship between KE, and 'm' and 'v':-

$\boxed{KE = \frac{1}{2} mv^2}$

∴ KE = ½(12 kg)(20 m/s)²

⇒ KE = (6 kg)(400 m/s² × m)

⇒ KE = 2400 Nm or 2400 J

⇒ KE = 2.4 J (answer)

More:-

• Kinetic energy is the energy possessed by an object due to it's virtue of it's motion.
• Energy is of many types, for e.g.,

1. Mechanical Energy (KE + PE),
2. Electrical energy,
3. Chemical energy,
4. Light energy,
5. Acoustic energy, etc.

Answer 2

Answer:

From (i) and (ii), v_1=4cm/s,v 2=16cm/s,

Loss in K.E. =1/2m 1u12−1/2(m 1 )v 12−1/2m 2v 22

=1/2×1.2(20/100) 2 −1/2(1.2)(4/100) 2

−1/2×1.2(16/100) 2=2.4×10 −2 −0.096×10 −2

−1.536×10 −2

Loss in K.E.=0.768×10 −2=7.7×10 −3 J

Here, m¹ =1.2kg,u¹=20cm/s,m² =1.2kg,u² =0

If v¹ and v² are velocities of the two blocks after collision, then according to principle of momentum

→velocity of approach =u 1 −u 2=20cm/s

→velocity of separation=vv −v1

By definition, e=v 2 −v 1 /u 1−u2=3/5=vv −v1 /u1−u 2

From (i) and (ii), v_1=4cm/s,v 2 =16cm/s,

→Loss in K.E. =1/2m 1u 12 −1/2(m 1 )v 12

−1/2m 2 v 22

=1/2×1.2(20/100) 2

−1/2(1.2)(4/100) 2

−1/2×1.2(16/100) 2

=2.4×10 −2−0.096×10 −2 −1.536×10 −2

→Loss in K.E.=0.768×10 − 2=7.7×10 −3J

Explanation:

hope it helps you see