# Physics Graph question -- Pushing a block on a frictionless surface

1. Oct 27, 2014

### Bdb1331

The diagram shows how a force along the x axis varies with location. A block of mass 7.20 kg moves along the x axis on a horizontal frictionless surface, influenced by this force. (Graph is attached)
A) How much work is done by the force as the block moves from the origin to 8.0 m?

B) If the block has a velocity of 3.80 m/s at the origin, what is its velocity at 8.0 m?

For part A, I worked out the work to be 33 J by finding the area under the curve...
in the first two seconds

W = F(avg)d
W = [(2 + 8) / 2](2 - 0)
W = 10 J

from 2 to 4 seconds

W = [(8 + 4)/2] (4 - 2)
W = 12 J

from 4 to 6 s

W = 4(6 - 4)
W = 8 J

from 6 to 8 s

W = [(4 + -1)/2](8 - 6)
W = 3 J

Total work

W = 10 + 12 + 8 + 3
W = 33 J

But I am sorta lost when it comes to B)

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2. Oct 27, 2014

### PhanthomJay

Are you familiar with work-energy relationships?

3. Oct 27, 2014

### Bdb1331

Sorta, but not exactly confident in my skills

4. Oct 27, 2014

### PhanthomJay

Well, just try using the work - energy theorem. What does that theorem say?