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Question :
71. A speed boat requires 80 kW to move at : 2102113

71. A speed boat requires 80 kW to move at a constant speed of 15 m/s. What is the resistive force of the water at this speed?

A. 2 700 N

B. 5 300 N

C. 6 500 N

D. 7 700 N

72. Water flows over a section of Niagara Falls at a rate of 1.20 ยด 10^{6} kg/s and falls 50.0 m. What is the power dissipated by the waterfall?

A. 588 MW

B. 294 MW

C. 147 MW

D. 60.0 MW

73. A 1 000-kg sports car accelerates from zero to 25 m/s in 7.5 s. What is the average power delivered by the automobile engine?

A. 20.8 kW

B. 30.3 kW

C. 41.7 kW

D. 52.4 kW

74. A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface. As the speed of the mass increases at a constant acceleration, the power delivered to it by the force:

A. remains the same.

B. increases.

C. decreases.

D. doubles every 4.0 seconds.

75. A 100-W light bulb is left on for 10.0 hours. Over this period of time, how much energy was used by the bulb?

A. 1 000 J

B. 3 600 J

C. 3 600 000 J

D. 1.34 hp