I have a couple of questions for physics. please, please, I beg you HELP!!!!!?
1) A winch that's powered by a 156 W motor lifts a crate 9.8 m in 11s. What is the mass of the crate?
2)A man exerts a force of 310 N on a lever to raise a crate with a mass of 910 kg. If the effiency of the lever is 78%, what is the lever's IMA?
3) A worker uses a pulley to lift a 45kg object. If the mechanical advantage of the pulley is 5.2, what is the effort force exerted by the worker?
4)John pushes a crate across the floor of a factory with a horizontal force. The roughness of the floor changes, and John must exert a force of 20N for 5m, then 35N for 12m, then 10N for 8m. Find the work John does pushing the crate.
5)A lawn mower is pushed across a lawn by a force of 115N along the direction of the handle, which is 22.5 degrees above the horizontal. If 64.6W of power is developed for 90s, what distance is the roller pushed?
1. P = E/t = mgh/t
solving for m, m = Pt/gh = (156 x 11) / (9.8 x 9.8) = 17.87kg
2. I think you mean the AMA, given that you quote the friction...
310N in, so 310 x 0.78 = 241.8N
The weight on the far end is mg = 910x9.8 = 8918N
the AMA is the ratio, 8918/241.8 = 36.88
If you really did mean IMA, 8918/310 = 28.76.
You may wonder why the AMA is greater than the IMA. It's because you need to change the lever to be able to lift the mass. Normally in these questions you start with a given lever and work it out from there.
3. w = mg = 45 x 9.8 = 441N
The mechanical advantage is 5.2 so,
441 / 5.2 = 84.8N
4. Work = Force x Distance ...
Work = (20x5) + (35x12) + (10x8) = 600J
5. Horizontal force = 115 Cos 22.5 = 106.24N
E = Pt = 64.6 x 90 = 5814J
Distance = Work / Force = 5814 / 106.24 = 54.7m
