A test rocket at ground level is fired straight up from rest with a net upward acceleration of 20 m/s².After 4.0 s,the motor turns off but the rocket continues to coast upward with insignificant air resistance.What maximum elevation does the rocket reach? A)160 m B)330 m C)320 m D)410 m E)490 m

Question

Quizplus · Accepted Answer

The rocket accelerates for 4 seconds, reaching a velocity of 80 m/s (v = at = 20 m/s² * 4 s). The distance covered during this time is 160 m (s = 0.5 * a * t² = 0.5 * 20 m/s² * (4 s)²). After the motor turns off, the rocket continues upward until its velocity becomes zero. Using v² = u² + 2as, where v = 0, u = 80 m/s, and a = -9.8 m/s² (gravity), the additional height is 320 m. The total maximum elevation is 160 m + 320 m = 480 m.

A Test Rocket at Ground Level Is Fired Straight Up