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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Two charged bodies separated by a distance d exert an electrical force on each other. The charge on one of the bodies is doubled. The electrical forces on each body now
a. double b. decrease by 1/2 c. stay the same d. differ—the force on the other body doubles, but the force on the body whose charge was changed stays the same as before e. increase by a factor of four
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
A 2.00 kg mass is connected to a spring with a spring constant of 9.00 N/m. The displacement is given by the expression x(t) = 12.0 cm sin
What is the period of the simple harmonic motion?
A. 4.75 sec B. 4.27 sec C. 3.95 sec D. 3.36 sec E. 2.96 sec
A string of length L with fixed ends is made to go into standing wave patterns. What is the longest wavelength associated with all possible standing wave patterns in this situation?
a. L/4 c. L b. L/2 d. 2L