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Question :
71. When a collision perfectly inelastic, then:
A. all the kinetic : 2102130

71. When a collision is perfectly inelastic, then:

A. all the kinetic energy is conserved.

B. all the kinetic energy is gone.

C. the participants stick together.

D. the total momentum is zero.

72. A model car is propelled by a cylinder of carbon dioxide gas. The cylinder emits gas at a rate of 4.5 g/s with an exit speed of 80.0 m/s. The car has a mass of 400 g, including the CO_{2} cylinder. Starting from rest, what is the car's initial acceleration?

A. 0.90 m/s^{2}

B. 4.5 m/s^{2}

C. 9.0 m/s^{2}

D. 36 m/s^{2}

73. A 1 000-kg experimental rocket sled on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." If the rocket, initially at rest, moves at 150 m/s after the burn, what impulse is experienced by the rocket sled?

A. 1.1 ´ 10^{5 }kg?m/s

B. 1.6 ´ 10^{5} kg?m/s

C. 1.5 ´ 10^{5} kg?m/s

D. 1.9 ´ 10^{5} kg?m/s

74. A 1 000-kg experimental rocket sled at rest on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." The rocket moves at 150 m/s after the burn. What average force is experienced by the rocket during the burn?

A. 0.95 ´ 10^{4} N

B. 0.75 ´ 10^{4} N

C. 0.60 ´ 10^{4 }N

D. 0.35 ´ 10^{4} N

75. A helicopter stays aloft by pushing large quantities of air downward every second. What mass of air must be pushed downward at 40.0 m/s every second to keep a 1 000-kg helicopter aloft?

A. 120 kg

B. 245 kg

C. 360 kg

D. 490 kg