A lever enables you to lift objects that are too heavy to lift by hand. The leve

Question

A lever enables you to lift objects that are too heavy to lift by hand. The lever pictured here consists of a long board placed on a pivot. To lift the concrete slab on the left end of the board, the person pushes downward on the right end.

A. Using the concept of torque, explain why a lever makes it easier to lift the heavy slab. Hint: in order for the board to "swing" clockwise, thereby lifting the slab, how must the torque exerted by the person on the board compare to the torque exerted by the slab on the board?

B. The slab weighs 1000 Newtons. The segment of the board to the right of the pivot is 5 times longer than the segment of the board to the left of the pivot. Assuming the board is very light, how hard must the person push down on the right end of the board to lift the slab?

C. A student last year gave this explanation for why this lever works:
"if you take the slab off the board, and if the student lets go of the board,the board will naturally swing clockwise; it ends up with its right end on the ground. thats because the weight of the board to the right of the pivot is greater than the weight of the board to the left of the pivot. My point is, even with the slab in place, the weight of the board "helps" the student make the board swing clockwise. Thats why the students force on the board can be less than the slabs weight"

In what ways do you agree or disagree with this explanation? hint: itll help to check for coherence between your answer here and your answers to A and B.


PLEASE PLEASE PPLEAASEE HELP ME ANSWER THIS!! I HAVE ABSOLUTELY NO CLUE ON HOW TO START. BUT PLEASE ,IF YOU ANSWER THIS, BE GOOD AT EXPLAINING THOROUGHLY, MY TA WILL SERIOUSLY TAKE POINTS OFF FOR THE SLIGHTEST THING. SORRY FOR SUCH LONG QUESTION. :/ THANKS IN ADVANCE

Explanation / Answer

A. Torque is defined by torque=Force*perpendicular distance from the applied force. So, if you apply a 10N force downward at the end of a 5m long rod, the torque would be 50 N*m's. Now, if a block was at the other end of a rod, it too is applying its own torque, but lets say the pivot (think of a see-saw, the pivot is what the plank is rotating on) was much shorted on the block's side. So if a 10N block only had one meter of plank, it's toque would only be 10N*m's. So, you would only need to apply 2Ns at the end of your 5m side to match the 10N*m torque that the block was applying. (10N*1m=2N*5m)

B. This one is easy. 1000N(1m)=XN(5m). X=200N.

C. The student is partially right, since the level has more mass on one end, it ends up applying a torque (since it has more weight, and a larger perpendicular distance to apply the force) but that is a symptom of torque rather than the effect of it. Essentially, the force that you apply downward is multiplied by the ratio of length between your side and the other side of the lever to move something on the other end of it.

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