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History Bookmarks People Window Help eChegg.com 2Pac-Still West Side expertta.com/Common/TakeTutorialAssignment.aspx Class Management I Help IW06 Begin Date: 1/ /10/2016 12:00:00 AM-Due Date: 2/26/2016 11:59.00 PM End Date: 5/10/2016 11:5900 PM (8%) Problem 1:A car is being lifted by a crane so that it moves upwards at a constant speed. 50% Part (a) What interaction is doing negative work to the car as it is being lifted? 50% Part (b) what interaction is doing positive work to the car as it is being lifted? There is no work being done because the kinetic energy of the crate is constant The weight of the car acting on the rope The cars gravitational interaction with the Earth. The car's contact interaction with the rope. Grade Deduct Potenti Submi Attemp Submit Hint I give up! Hints: 2% deduction per hint. Hints remaining:- Feedback: 2%.dohction per feedback.

Explanation / Answer

(a)

The work done by a force is,

W=Fscos(theta), here, theta is the angle between direction of forcce acting and direction of the motion of the object.

The gravitational pull on the car always acts vertically downwars. The car is moved in opposite to the gravitational pull. So, theta is equal to 180. thus, the work done by the gravitaional interaction is negative.

(b)

The car is lifted. According to the work-energy theorem, the work done on the car is equal to the change in its potential energy. This work is done by the car's contact interaction (tension in the rope) with the rope is positive.

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