Grade 11Mechanics

A bag of sand of mass 2 kg is suspended by a rope. A bullet of mass 10g is fired at it and gets embedded into it. The bag rises up a vertical height of 10 cm. The initial velocity of the bullet is nearly-

a) 70 m/s
b) 140 m/s
c) 210 m/s
d) 280 m/s

Guntaas Brar

7 Years agoGrade 11

2 Answers

Agrata Singh

7 Years ago

Writing energy conservation for the system just before collision and when the bag reaches height of 10 cm

E_initial= 1/2x0.01v²( only the bullet had kinetic energy)

E_final=(2+0.01)x0.1x10 (potential energy of bag+bullet at height 10 cm)

Upon solving E_initial=E_final you will get

V²=402

v=20(approx)

Suraj

7 Years ago

By conservation of energy,

1/2mv^2=mgh

(m gets cancelled)

1/2v^2= 10 × 0.01 (Taking g=10m/s^2, h=0.01m

V=√0.2-------------1

By conservation of momentum,

Mass of bullet × velocity of bullet = (Mass of bullet +mass of bag) × velocity of bag

0.01kg × velocity of bullet = (0.01 + 2) × √0.2

Velocity of bullet= 2.75/0.01

= 280(approx)

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A bag of sand of mass 2 kg is suspended by a rope. A bullet of mass 10g is fired at it and gets embedded into it. The bag rises up a vertical height of 10 cm. The initial velocity of the bullet is nearly- a) 70 m/sb) 140 m/sc) 210 m/sd) 280 m/s

Guntaas Brar

2 Answers

Agrata Singh

Suraj

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