Question

How much minimum power output does a toy rocket need to maintain a constant upwards velocity of $4.00m/s$? Neglect air resistance.

• A. $0.00W$
• B. $4.00W$
• C. $9.81W$
• D. $39.24W$
• E. Not enough information

Answer 1

The correct option is E Not enough information

A constant gravitational force acts vertically downwards on the rocket, hence to maintain a constant velocity, a force equal to the constant gravitational force must be applied vertically upwards.

Since the force would be constant, the power of the force would be $\frac{dW}{dt}=\frac{d\left(Fh\right)}{dt}=mg\frac{dh}{dt}=mgv$

Hence the mass of the rocket needs to be known.