If the pole-vaulter were to land on concrete rather than on a cushion, the impulse that stops the fall would be:
a. greater because of the rigidity of the concrete.
b. greater because the force of impact is greater.
c. less, because there is less change in momentum during the stop.
d. less, because he would come to a stop over a shorter period of time.
e. the same because impulse is the change in momentum of the object.
e
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A 0.20-km wide river has a uniform flow speed of 3.0 m/s toward the east. A boat with a speed of 8.0 m/s relative to the water leaves the south bank and heads in such a way that it crosses to a point directly north of its departure point. How long does it take the boat to cross the river?
A. 29 s B. 23 s C. 25 s D. 27 s E. 17 s
Which of the following describes tectonics?
A) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface B) the eruption of molten rock from a planet's interior to its surface C) the disruption of a planet's surface by internal stresses D) the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
A projectile is projected from the origin with a velocity of 45.0 m/s at an angle of 30.0 degrees above the horizontal. What is the velocity when the projectile hits the ground?
A. Vx = 35.7 m/s, Vy = -22.5 m/s B. Vx = 39.0 m/s, Vy = -22.5 m/s C. Vx = 35.7 m/s, Vy = -39.0 m/s D. Vx = 39.0 m/s, Vy = -35.7 m/s E. Vx = 22.5 m/s, Vy = -22.5 m/s
Two very long parallel wires are a distance d apart and carry equal currents in opposite directions. The locations where the net magnetic field due to these currents is equal to zero are
A) midway between the wires. B) a distance d/2 to the left of the left wire and also a distance d/2 to the right of the right wire. C) a distance d to the left of the left wire and also a distance d to the right of the right wire. D) a distance d/ to the left of the left wire and also a distance d/ to the right of the right wire. E) The net field is not zero anywhere.