Hw 6 Solution - reyes (mr29667) Homework 6 chelikowsky...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: reyes (mr29667) Homework 6 chelikowsky (59005) 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Batman, whose mass is 78 . 8 kg, is holding on to the free end of a 15 . 8 m rope, the other end of which is fixed to a tree limb above. He is able to get the rope in motion as only Batman knows how, eventually getting it to swing enough that he can reach a ledge when the rope makes a 77 . 7 angle with the vertical. The acceleration of gravity is 9 . 8 m / s 2 . How much work was done against the force of gravity in this maneuver? Correct answer: 9602 . 12 J. Explanation: The work done is given by the expression, W = m g y . The change in height, y , is y = - cos . Thus W = mg ( - cos ) = mg (1- cos ) = (78 . 8 kg) (9 . 8 m / s 2 ) (15 . 8 m) (1- cos 77 . 7 ) = 9602 . 12 J . 002 10.0 points A force F is exerted by a broom handle on the head of the broom, which has a mass m . The handle is at an angle to the horizontal, as shown below. F What is the work done by the force on the head of the broom as it moves a distance d across a horizontal floor? 1. W = F d cos correct 2. W = F d sin 3. W = F md sin 4. W = F m cos 5. W = F m tan Explanation: By definition, the work done by a force is given by the formula W = vector F vector d = F d cos , where vector d is the displacement vector, and is the angle between vector F and vector d . Simply apply the definition, the work is W = F d cos . 003 10.0 points You drag a(n) 19 . 3 kg steamer trunk over a rough surface by a constant force of 162 N acting at an angle of 30 . 1 above the horizon- tal. You move the trunk over a distance of 7 . 99 m in a straight line, and the coefficient of kinetic friction is 0 . 186. The acceleration of gravity is 9 . 8 m / s 2 . 19 . 3 kg = 0 . 186 1 6 2 N 3 . 1 How much is the work done on the block by the net force? Correct answer: 959 . 487 J. Explanation: reyes (mr29667) Homework 6 chelikowsky (59005) 2 F mg n f k Work is W = vector F vectors , where vectors is the distance traveled. In this problem vectors = 5 x is only in the x direction. W F = vector F x vectors x = F s x cos = (162 N) (7 . 99 m) cos30 . 1 = 1119 . 83 J . To find the frictional force, F friction = N , we need to find N from vertical force balance. Note: N is in the same direction as the y component of F and opposite the force of gravity. Thus F sin + N = mg , so that N = mg- F sin . Thus the friction force is vector F friction =- N x =- ( mg- F sin ) x , and the work done by friction is W = vector F friction vectors =-| F f | | s | =- ( mg- F sin ) s x =- . 186 bracketleftBig (19 . 3 kg) (9 . 8 m / s 2 )- (162 N) sin30 . 1 bracketrightBig (7 . 99 m) =- 160 . 347 J ....
View Full Document

Page1 / 9

Hw 6 Solution - reyes (mr29667) Homework 6 chelikowsky...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online