Question

Q2. Two bodies of equal masses move with the uniform velocities v and 3v respectively. Find
the ratio of their kinetic energy?

Answer 1

Answer:

Answer

Mass of first body =m

Velocity of the first body =v

Mass of second body =m

Velocity of second body =3v

The ratio of kinetic energies of the two bodies =

Kineticenergiesofsecondbody

Kineticenergiesoffirstbody

=

2

1

m(3v)

2

2

1

mv

2

=

2

9

mv

2

2

1

mv

2

=

9

1

The ratio of the kinetic energies =1:9

Answer 2

Explanation:

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We know that kinetic energy is given as

E = (1/2)mv2

now,

for body 1

E1 = (1/2)mv2

and

for body 2

E2= (1/2)m(3v)2

= (9/2)mv2

so,the ratio will be

E1/E2 = [(1/2)mv2] / [(9/2)mv2]

thus,

E1/E2 = 1/9

The ratio of the kinetic energies =1:9