question E. 16 1 A rifle with a mass of 0.9 kg fires a bullet with a mass of 6.0

Question

question E. 16

1 A rifle with a mass of 0.9 kg fires a bullet with a mass of 6.0 g (0.006 kg). The bullet moves with a muzzle velocity of 750 m/s after the rifle is fired a. What is the momentum of the bullet after the rifle is fired? b. If external forces acting on the rifle can be ignored, what E17 is the recoil velocity of the rifle? E13. A rocket ship at rest in space gives a short blast of its engine, firing 50 kg of exhaust gas out the back end with an average velocity of 400 m/s. What is the change in momen- tum of the rocket during this blast? E18 E14. A railroad car with a mass of 11 000 kg collides and cou- ples with a second car of mass 19 000 kg that is initially at rest. The first car is moving with a speed of 4.5 m/s prior to the collision a. What is the initial momentum of the first car? b. If external forces can be ignored, what is the final velocity E19 of the two railroad cars after they couple? E15. For the railroad cars in example box 7.4. a. What is the kinetic energy of car 5 before the collision? b. What is the kinetic energy of all five cars just after the collision? c. Is energy conserved in this collision? E16. A 4000-kg truck traveling with a velocity of 20 m/s due south collides head-on with a 1350-kg car traveling with a velocity of 10 m/s due north. The two vehicles stick together after the collision a. What is the momentum of each vehicle prior to the collision? synthesis problems SP3 SPI. A fast ball thrown with a velocity of 40 m/s (approximately 90 MPH) is struck by a baseball bat, and a line drive comes back toward the pitcher with a velocity of 60 m/s. The ball is in contact with the bat for a time of just 0.04 s. The base- ball has a mass of 120 g (0.120 kg) a. What is the change in momentum of the baseball during b. Is the change in momentum greater than the final e. What is the magnitude of the impulse required to pro- this process? momentum? Explain. duce this change in momentum?

Explanation / Answer

(E.16) Solve this problem using the principle of conservation of momentum.

Take the south direction as positive.

So, north direction will be negative.

So, total initial momentum of the car, Pi = m1*v1 + m2*v2

= 4000 kg * 20m/s + 1350 kg* (-10 m/s)

= 66500 kg*m/s

Suppose the final velocity of both the vehicles (after stick togather) is V.

So, final momentum Pf = (m1 + m2)*V

Equalize the two -

Pi = Pf

=> m1*v1 + m2*v2 = (m1 + m2)*V

=> 66500 kg*m/s = (4000 kg + 1350 kg)*V

=> V = 66500 kg*m/s / (4000 kg + 1350 kg) = 12.43 m/s

Positive sign in the velocity shows its direction towards south.

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