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A toy rocket, launched from the ground

0 votes
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A toy rocket, launched from the ground, rises
vertically with an acceleration of 39 m/s^2
for 14 s until its motor stops.

Disregarding any air resistance, what maximum height above the ground will the rocket
achieve?

The acceleration of gravity is
9.8 m/s^2

Answer in units of km
asked Sep 15, 2014 in AP Physics C by anonymous

1 Answer

0 votes
For the first 14 seconds, it is accelerating upwards at 39 m/s^2, with which one can find its height when the rocket just stops. ||y_1=\frac 12 at_1^2||

After ||t_1|| (14 s), it going into an accelerated motion with -9.8 m/s^2. Use ||v_f^2-v_i^2=-2gy_2||, one can find how much additional height it can reach. Here ||v_f=0||, ||v_i=at_1||.

Total height is ||y_1+y_2||.
answered Sep 15, 2014 by PhysicsDude (21,750 points)
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