A toy rocket of mass 0.1 kg hass a small fuel of mass 0.02 kg, which it burns out in 3s. Starting from rest on a horizontal smooth track, it gets a speed of `20ms^(-1)` after the fuel is burnt out. What is the approcimate thrust of the rocket ? What is the energy content per unit mass of the fuel ? (Ignore the small mass variation of teh rocket during fuel burning).

Explanation

Here,`M=0.1kg, m=0.02kg, t=3s,`
`u=0,upsilon=20m//s, Thrust=?, en ergy//mass=?`
Thrust of rocket,
`F=Ma=(M(upsilon-u))/(t)=(0.1(20-0))/(3)=(2)/(3)N`
KE gained by rocket `=(1)/(2)Mupsilon^(2)=(1)/(2)xx0.1(20)^(2)`
`=20J`
Energy `//` mass of fuel`=(20)/(0.02)=1000Jkg^(-1)`