Force Problems with Motion Video Lessons

Concept

# Problem: A helicopter of mass M is lowering a truck of mass m onto the deck of a ship, (a) At first, the helicopter and the truck move downward together (the length of the cable doesn't change). If their downward speed is decreasing at a rate of 0.467 g, what is the tension in the cable? T = ______ mg (b) As the truck gets close to the deck, the helicopter stops moving downward. While it hovers, it lets out the cable so that the truck is still moving downward. If the truck's downward speed is decreasing at a rate of 0.467 g, while the helicopter is at rest, what is the tension in the cable? T = ______ mg

###### FREE Expert Solution

Newton's second law:

$\overline{){\mathbf{\Sigma }}{\mathbf{F}}{\mathbf{=}}{\mathbf{m}}{\mathbf{a}}}$

(a)

We'll consider the forces on the track to solve this problem.

The weight of the truck is downward, the tension is upward, the acceleration is opposite the velocity (upward).

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###### Problem Details

A helicopter of mass M is lowering a truck of mass m onto the deck of a ship,

(a) At first, the helicopter and the truck move downward together (the length of the cable doesn't change). If their downward speed is decreasing at a rate of 0.467 g, what is the tension in the cable?

T = ______ mg

(b) As the truck gets close to the deck, the helicopter stops moving downward. While it hovers, it lets out the cable so that the truck is still moving downward. If the truck's downward speed is decreasing at a rate of 0.467 g, while the helicopter is at rest, what is the tension in the cable?

T = ______ mg