1,001 questions about the ASTB (post your scores & ask your questions here!)

[ea6bflyr]

I originally had this same line of reasoning, but fixed pulleys don't have as much of a mechanical advantage as movable pulleys.

Seeing both pulleys are moving the same weight across the same distance on the same ramp, I'd figured the one with the greater mechanical advantage would require less force (i.e. pulley B because it's a movable pulley with a MA = 2 (the two string segments) whereas pulley A has an MA of 1 (fixed pulley always has MA = 1)

The fixed pulley will make the weight more difficult to move. The moveable pulley will make the weight easier to move.

Movable pulleys give you a mechanical advantage, which is measure of performance for machines. Having a mechanical advantage means the force applied by the system is greater than the force you put in. In a pulley system, this means the pulley can lift or move the object with a greater amount of force than you apply to the rope. This allows you to lift or move heavy things more easily.

Here’s the catch—even though the moveable pulley system and the compound pulley system let you lift or move a heavy object with less force than you’d have to use with a fixed pulley, you still had to move the rope farther. The force exerted on the weight may have been increased, but you still had to perform the same amount of work on the rope. What this means is that even if the weight felt half as heavy with a moveable pulley, you’d have the pull the rope twice as far to raise it the same distance as a fixed pulley would!

 

[sevenhelmet]

The question wasn't about work, it was about force. The pulley on the right should require approximately half the force of the one on the left in order to move the weight up the ramp. Whether you're pulling the rope "uphill" or "downhill" to move the weight is irrelevant.

 

[Andre12]

But the pulley in the second one is not fixed.

 

[GunnarB]

Let’s say I only get a few question on Mech Comp correct and do well on the rest of the ASTB, is it possible I get at least a 777. I am going for SNA, but I cannot come to comprehend a lot of Mech Comp. And does your OAR go into play for SNA?

 

[NKMess]

Let’s say I only get a few question on Mech Comp correct and do well on the rest of the ASTB, is it possible I get at least a 777. I am going for SNA, but I cannot come to comprehend a lot of Mech Comp. And does your OAR go into play for SNA?

My understanding is that the OAR score isn't that important. With that said, if the board is close, your OAR score will become more important if the board needs to edge one candidate over another. I would just take the time to learn the concepts in the mech comp.