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In: Physics

A friend tells you that you have to do less work lifting a heavy box filled...

A friend tells you that you have to do less work lifting a heavy box filled with textbooks if you use a system of pulleys instead of just lifting the box and carrying it upstairs. Is your friend's statement correct? Why or why not? How do you correct your friend if the statemnet is incorrect.

Solutions

Expert Solution

As you know Work done=Force*displacement. If you are using multiple pulleys or using a system of pulleys then you are making the job easier. If you are using just one pully then around the same amount of force you are applying for to lift the weight. In the case of a compound pulley, you are reducing the force required to lift the box as the weights are distributed. The price you pay here is to increase your distance and constantly exerting the same force over that distance. For example, in order to reduce the force, you must exert half the load's weight, then in order to lift the load one meter, you will need to pull the rope two meter. So finally the displacement is same in both pulley and hand lifting case .so in case of compound pulley the work done will be less as the force is less.

genius_generous answered 2 years ago
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