83) A toy rocket is launched vertically from ground level at time t = 0 s. The rocket engine
provides constant upward acceleration during the burn phase. At the instant of engine burnout,
the rocket has risen to 49.0 m and acquired an upward velocity of The rocket continues
to rise with insignificant air resistance in unpowered flight, reaches maximum height, and falls
back to the ground. The maximum height reached by the rocket is closest to
A) 233 m.
B) 221 m.
C) 209 m.
D) 244 m.
E) 256 m.
84) A rock is projected upward from the surface of the Moon, at time t = 0 s, with an upward
velocity of 30.0 m/s. The acceleration due to gravity at the surface of the Moon is 1.62 m/s2, and
the Moon has no atmosphere. The height of the rock when it is descending with a speed of 20.0
m/s is closest to
A) 115 m.
B) 125 m.
C) 135 m.
D) 145 m.
E) 154 m.
85) A ball is thrown straight upward from ground level with a speed of How much time
passes before the ball strikes the ground if we disregard air resistance?
A) 3.7 s
B) 1.8 s
C) 1.1 s
D) 0.6 s
86) A rock is thrown directly upward from the edge of a flat roof of a building that is 56.3 meters
tall. The rock misses the building on its way down, and is observed to strike the ground 4.00
seconds after being thrown. Take the acceleration due to gravity to have magnitude and
neglect any effects of air resistance. With what speed was the rock thrown?
87) A package is dropped from a helicopter that is moving upward at If it takes
before the package strikes the ground, how high above the ground was the package when it was
released? Neglect air resistance.