Forces and Motion

Rocket Flying - Calculations.

Q.  A stationary rocket was moving at 240 m/s 2 minutes after take off.
What was its acceleration?

A.  Use   a = (v-u) ÷ t

v = 240 m/s
u = 0
(because the rocket was stationary, its initial velocity was 0)
t = 2 x 60
(changing minutes into seconds)

        a = (240 - 0) ÷ (2 x 60)
= 240 ÷ 120  
= 2·0 m/s2       

Q.  The rocket has a mass of 1500 kg.
What force was needed to give it the acceleration of 2·0 m/s2 ?

A.  Use   F = m x a

F = 1500 x 2
  = 3000 N.

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