Somewhat easy work/engery problem?

Question

Need some help with this:
10 square blocks, each of mass 1kg are to be stacked up on a floor to make a piloe 50cm high - assuming that the block are initially all lying on the floor and assuming they have the same dimensions, how much work is done in stacking up the bricks.

Can anyone help me with some guidance please!

Thanks Ed, but where do I get the force from?

Answer 1

Work equal to force you apply getting a brick into particular position times the path parallel to that force.

W=Fs

W=sum of Wi
Wi=Fi si Does that help?

Lets do it for one brick

Lets say you lifted that brick from the floor 0.5 m, moved it 10 m and place it on a pedestal 0.20 m above the floor. While you have moved it you accelerated for 1 s and the decelerated 1 s with acceleration 0.5m/s^2.

1. work done to lift to .5m W1= mgh1 h1=0.5m
2. W2= W3 work done to accelerate = work done to deccelerate and they cancel each other out.
3. wok done on placing the brick W4 = -mgh2 ; h2= 0.30m

Work total = Wt=W1+W2+W3+W4
Wt= mgh1 +W2 -W2 -mgh2
Wt= mg(h1-h2)

Now lets get back to your problem.
It says to make a pile 50 cm high. Am I to suppose that each brick is 5cm high? if so

Wt= W1+W2+W3+W4...
W1= mgh h=0 so W1=0
W2=mgh2 h=0.05m
W3= mgh3 h=0.10m

you got the idea? in general

Wt=(0+ mgh2+mgh3+...mgh10)
Wt=mg(0 + h2 + h3+...h10) h2=h1+0.05
Wt=mg(0 + h2+ h2+... (10-1) 0.05) and since h2=0.05=h
Wt=10mgh=10 (1) 9.81 x 0.05=4.9 J