Here's the question:

A rocket is launched vertically. For the first 6 s it accelerates 150ms-2.

a) calculate it's speed at the end of this time, and the distance covered.

b) the rocket continues it's flight acted upon only by gravioty. Calculate how long it takes to reach the top of it's flight and the further distance covered.



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a) basically what I did here, to find the speed of it, I multiplied the acceleration by the seconds. Increases speed every 6 seconds so, end velocity = 900ms-1. The problem I have here is that I did not consider gravity (-9.81 since the rocket is moving upwards).

distance covered = some random equation = 2,700m...

b) what I did here was wrong... so wrong...

Help please

a) if you think you should take gravity into account that's easy, total acc. Upwards is 150-9.8, do the same as you did.

equation for distance = s = ut+0.5at^2

b) should be simple suvat equations here too

v^2 = u^2 + 2as? Yeah that'll do it.

and for time s = 0.5(u+v)t

For part a), you don't need to worry about gravity... since it's accelerating at a certain rate, the effect of gravity should already be handled. Acceleration is the net effect of all forces acting on an object. 2700 is the correct answer for that.

For b), once the rocket stops accelerating, you have it continuing upwards until v = 0. This continues for v/a seconds. That will give you the time, and you already have the start and end velocities.