Question

Will Fan and medal.

I have a few Physics calculations on a worksheet and was wondering if anyone would mind checking my answers. Thanks!

Note: All answers must be expressed in significant digits.


While mowing your lawn, you push a lawnmower with a constant force of 300. N. How much work have you done, assuming all force is in the same direction as the direction of motion?

My Answer: 36000 Joules

An elevator lifts a person 24.4 m with a force of 300. N in 15.0 seconds. what is the power of the elevator?

My Answer: 490 J

Answer 1

hold on...

Answer 2

I'm not sure, but both seem right.

Answer 3

Thank yous so much!

Answer 4

im not sure though.

Answer 5

Thanks!

Answer 6

What's the distance that it gave you for a? Can't tell if it's correct or not because we're not given enough information.

b). Seems about right

Answer 7

In the second scenario, the motion is opposed to the force of gravity, hence work is performed.

However in the first scenario, the motion is perpendicular to the force of gravity, no work is performed.

Answer 8

@UnkleRhaukus It's not asking about the work due to gravity. It's asking how much work have *you* done. If the force you exert on an object is parallel to the motion of that object, then you are doing work on that object.

Answer 9

What forces oppose the motion? none have been specified.

Answer 10

If potential energy has not been achieved, no work has been performed.

Answer 11

From all the courses I've had that involve work, we can define it as\[\huge \text{W}=\vec{\text{F}} \cdot \vec{\text{r}}\]
There's nothing in that equation that specifies opposite forces. The work due to gravity for displacement that is perpendicular to gravity is 0.

Answer 12

From Work-Energy Principle:
\[\huge \text{W}=\Delta \text{KE}\]

Answer 13

Net work, that is.

Answer 14

When the radial vector is in the opposite direction to the force, \(W = Fr\).

When the radial vector is in the same direction as the force, \(W = -Fr\).

When the radial vector is perpendicular to the force, the dot product is zero.

Answer 15

But cos(180) (for displacement vector opposite of force vector) = -1. It looks like you have it switched?

Answer 16

W = work performed by you, (not work performed by the force field)

Answer 17

Yes, I realize that. If I apply a force on an object, and it moves parallel and in the same direction as the force vector, then it will yield W=Fr

Answer 18

That is something that I have done in multiple courses. I am not sure what you are still getting at.