Physics question on work, Force and displacement please help!!!!!!! Thanks. Please explain clearly, show steps

Question

1. A Farmer uses a horizontal force of magnitude on a wagon and moves it a horizontal displacement of magnitude 3.2m. How much work has the farmer done on the wagon?

2. A tow truck does 3.2 kJ of work in pulling horizontally on a stalled truck to move it 1.8 m horizontally in the direction of the force. What is the magnitude of the force?

3. A store clerk moved a 4.4 kg box of soap without accleration along a shelf by pushing it with a horizontal force of magnitude 8.1 N. If the employee did 5.9 J of work on the box, how far did the box move.

W=FD

im really confused on the last one, why doesn't the mass apply?

Answer 1

Hi,
The general equation for work is:
W=∫F·ds.....(F.dot. ds) and if the force is in the same direction as the displacement; then the work becomes:
W=F*d
Now, the only other thing we need to know is that 1 joule = 1N·m. So, we can just multiply force times distance and get joules so long as we have consistent units. Let's do the first one.
1) Well, you left out the force. Let's just assume that it's 10 Newtons.
W=10*3.2
= 32 joules.
You can plug in whatever number should have been in your problem and do the arithmetic.

2)...W=F*d
.......3200=F*1.8
.......F=3200/1.8
.......F=1777.78 Newtons

3) W=F*d
.....5.9=8.1*d
....5.9/8.1=d
....d = 0.7283...meters.