Question

a body of mass 2.0kg make elastic collision with another body at rest and continues to move in the original direction with a speed equal to half of its original speed . find the mass of the second body.
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Answer 1

Explanation:

m

1

=2 kg

u

1

=4 m/s

v

1

=

4

u

1

=

4

4

=1 m/s

u

2

=0

since nothing is given so we would take it as elastic collision.

hence conservation of momentum is given by:

m

1

u

1

+m

2

u

2

=m

1

v

1

+m

2

v

2

2×4+0=2×1+m

2

v

2

m

2

v

2

=6

according to the conservation kinetic energy:

2

1

m

1

u

1

2

+

2

1

m

2

u

2

2

=

2

1

m

1

v

1

2

+

2

1

m

2

v

2

2

2×16+0=2×1+m

2

v

2

2

m

2

v

2

2

=30

m

2

v

2

m

2

v

2

2

=

6

30

v

2

=5 m/s

m

2

=1.2 kg