A toy rocket is launched vertically from ground level at time t = 0.00 s.The rocket engine provides constant upward acceleration during the burn phase.At the instant of engine burnout,the rocket has risen to 64 m and acquired an upward velocity of 60 m/s.The rocket continues to rise with insignificant air resistance in unpowered flight,reaches maximum height,and falls back to the ground.The time interval during which the rocket engine provided the upward acceleration,is closest to
A)2.1 s.
B)2.3 s.
C)1.9 s.
D)1.7 s.
E)1.5 s.

Question

Quizplus · Accepted Answer

The correct answer is A because the rocket's initial velocity is 0 m/s, and its final velocity at burnout is 60 m/s. The acceleration during the burn phase is therefore (60 m/s - 0 m/s) / 2.1 s = 28.57 m/s^2. The time interval during which the rocket engine provided the upward acceleration is therefore 2.1 s.

A Toy Rocket Is Launched Vertically from Ground Level at Time