Net Force of a Model Rocket in Free Fall

[wicked_vixen]

A model rocket with a mass of 0.50 kg is fired vertically from the ground. Assume that it is streamlined enough that air resistance can be ignored. Suppose it ascends under the influence of a constant net force of 2.0 N acting in a vertical direction and travels for 6.0 s before its fuel is exhausted. Then it keeps moving as a particle-like object in free-fall as it continues upward, turns around, and falls back down.

What is the net force on the rocket when it continues upward as a free fall particle? as it turns around? When it is traveling back toward the ground?

 

[tiny-tim]

Welcome to PF!

Hi wicked_vixen! Welcome to PF!

… before its fuel is exhausted. Then it keeps moving as a particle-like object in free-fall as it continues upward, turns around, and falls back down.

What is the net force on the rocket when it continues upward as a free fall particle? as it turns around? When it is traveling back toward the ground?

What do you think?

What forces are acting on the rocket once the fuel stops?

Do they change, and if so, how?

 

[tomcue]

The net force on the model rocket when it continues upward as a free fall particle is zero. This is because in free fall, the only force acting on the rocket is the force of gravity, which is balanced out by the rocket's inertia.

When the rocket turns around, the net force on it is still zero. However, the direction of the net force changes from upward to downward as the rocket starts to fall back toward the ground.

When the rocket is traveling back toward the ground, the net force on it is now the force of gravity, which is equal to the rocket's weight. This is because the rocket is no longer expelling fuel and is now subject to the force of gravity pulling it toward the ground.