8. ) -/12 points SerCP11 6.1.P.005. 0/5 Submissions Used

Drops of rain fall perpendicular to the roof of a parked car during a rainstorm. The drops strike the roof with a speed of 18 m/s, and the mass of rain per second striking the roof is 0.040 kg/s.

(2) Assuming the drops come to rest after striking the roof, find the average force exerted by the rain on the roof.

magnitude

N

direction

-Select--- v

(b) If hailstones having the same mass as the raindrops fall on the roof at the same rate and with the same speed, how would the average force on the roof compare to that found in part (a)? (Assume the hailstones bounce back up off the roof.)

O The magnitude would be half that in part (a).

O The magnitude would be the same as in part (a).

O The magnitude would be one fourth times in part (a).

O The magnitude would be double that in part (a).

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9 .

-10 points SerCP11 6.2.P.022. 0/5 Submissions Used

A rifle with a weight of 20 N fires a 5.5-g bullet with a speed of 270 m/'s.

(a) Find the recoil speed of the rifle.

m/s

(b) If a 675-N man holds the rifle firmly against his shoulder, find the recoil speed of the man and rifle.

m/s

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10.

-46 points SerCP11 6.5.P.058. 0/5 Submissions Used

NASA's Saturn V rockets that launched astronauts to the moon were powered by the strongest rocket engine ever developed, providing 6.77 x 10 N of thrust while burning fuel at a rate of 2.63 x 10# kg/s. Calculate the engine's exhaust speed (in m/s).

HINT

m/'s

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