Question

3. James (26 kg) sits on a wheeled office chair (16 kg) holding a fire extinguisher (18 kg when empty). He points the discharge horn to the right and ejects 9 kg of carbon dioxide at 20 m/s. What is his speed and direction after the fire extinguisher is emptied (assuming friction is negligible)?

Answer 1

Solution;

Before the eject the moment of the system is 0 since its at rest and no velocity.

After the eject,the momentum due to carbon dioxide is;

$M_c×s=9×20=180$

Moment of the boy is ;

$M×v=(26+16+18)v$

Assuming equilibrium of the moments;

$M_cs+Mv=0$

$-180=60v$

$v=-30m/s$

Negative show the speed is in opposite direction to that of carbon dioxide ejection.