A rocket is fired upward from the earth's surface with acceleration 19.6 m s⁻². After 5 s its engine is switched off. The maximum height from the earth's surface is:
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Question

A rocket is fired upward from the earth's surface with acceleration 19.6 m s⁻². After 5 s its engine is switched off. The maximum height from the earth's surface is:

G1 Physics · Accepted Answer

During powered motion: a=19.6 m s⁻², t=5 s ⇒ v=98 m s⁻¹ and h₁=(1/2)at²=245 m. After engine cut-off, extra rise h₂=v²/(2g)=490 m. Total =735 m. Hence option D.