# Homework Help: Force and energy change

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1. Jan 31, 2016

### risa

1. The problem statement, all variables and given/known data
1.If the ship has a mass of 2.5 x 10^7 kg calculate the magnitude of the force acting on the ship during the deceleration.

I was trying to work that out using f=ma but that would
Make the force negative , is that possible

2. What is the nature of the force acting on the ship which leads to the deceleratipn and how does it cause the ship to slow down?

Could someone please explain how to do this one please and I also have no idea what "nature of a force" is

3. What is the main energy change as the ship slows down

Is the answer from kinetic to potential?
2. Relevant equations

3. The attempt at a solution

#### Attached Files:

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2. Jan 31, 2016

### Staff: Mentor

If the ship is decelerating, the force has to be in the opposite direction from the direction it is moving. So the force is negative.
The problem doesn't tell you what's causing the force. Maybe its a tug boat pulling back on the ship with a rope.
What's your understanding of the terms kinetic energy and potential energy?

3. Mar 29, 2016

### abcg

the force would be negative so the answer is 12.5 x 10^4 N
the force acting on the ship slowing it down is friction as the base of the ship is rubbing against the surface of the ocean.
not sure of the energy change though. i know its kinetic to something else...if you get the answer post it please

4. Mar 30, 2016

### haruspex

"Nature" might refer to the source of the force, its characteristics, or both.
Look at the statement at the very top of the attachment. What does it say?
Look at the shape of the graph. What does it tell you about the deceleration? What does that tell you about the force?