Question

A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 ms−1. To give an upward acceleration of 20 ms−2, the amount of gas ejected per second to supply the needed thrust is

Answer 1

Given :-

Mass of rocket = m = 5000 Kg

Velocity of rocket = u = 800 ms-¹

Acceleration of rocket = a = 20 ms-²

Acceleration due to gravity = g = 10 ms-²

As we know that by a relation When a body goes upward.

F = m(g+a)/u

F = 5000(10+20)/800

F = 50 × 30/8

F = 187.5 Kgs-¹.

Hence,

Amount of gas ejected = F = 187.5 Kgs-¹.

Some other information :-

This question is related to apparent weight of object in air.

When the body accelerates upward, the apparent weight of the body increases.

R - mg = ma

R = ma + mg

R = m(a + g).

Here, acceleration is in upward direction and acceleration due to gravity is acting in downward direction.