Bumpers on cars are not of much use in a collision. To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm
when the car had an initial speed of 2.0 m/s (about 4.5 mph). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.)
A) 3.2 × 104 N
B) 1.6 × 104 N
C) 5.4 × 104 N
D) 1.8 × 104 N
E) 6.5 × 105 N
B
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A. 4.75 sec B. 4.27 sec C. 3.95 sec D. 3.36 sec E. 2.96 sec
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a. L/4 c. L b. L/2 d. 2L
The ratio of the density of a material to the density of water is the
a. mass density b. weight density c. specific gravity d. buoyant force e. none of the above
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