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# a person is dragging a packing crate of mass 100 kg across a rough horizontal floor where the coefficient of kinetic friction is 0.400. he exerts a force f sufficient to accelerate the crate forward. at what angle above horizontal should his pulling force be directed in order to achieve the maximum acceleration?

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### James

Guys, does anyone know the answer?

get a person is dragging a packing crate of mass 100 kg across a rough horizontal floor where the coefficient of kinetic friction is 0.400. he exerts a force f sufficient to accelerate the crate forward. at what angle above horizontal should his pulling force be directed in order to achieve the maximum acceleration? from EN Bilgi.

## Solved A person is dragging a packing crate of mass 100 kg

Answer to Solved A person is dragging a packing crate of mass 100 kg Source : www.chegg.com

## Frictional forces and the angle for minimum frictional force

Homework Statement A person is dragging a packing crate of mass 100 kg across a rough floor where the coefficient of kinetic friction is 0.400. He exerts a... Forums Homework Help

Introductory Physics Homework Help

## Frictional forces and the angle for minimum frictional force

Thread starter Yam Start date Feb 26, 2015 Feb 26, 2015 #1 Yam

## Homework Statement

A person is dragging a packing crate of mass 100 kg across a rough floor where the coefficient of kinetic friction is 0.400. He exerts a force F just sufficient to keep the crate moving at a constant velocity. At what angle above the horizontal should his pulling force F be for it to be minimum?

## Homework Equations

Frictional Forces = UkN

## The Attempt at a Solution

Frictional Force = Uk(mg)(cosx)

Im stuck.

Feb 26, 2015 #2 BvU

I like the "I'm stuck" (you wouldn't post if you weren't). But

doesn't count as an attempt.

What forces play a role and how can you express the constant speed in an equation ?

Feb 26, 2015 #3 Yam

Forces that play a role:

1) Pulling force F 2) Frictional force

Constant speed means that there is no acceleration.

F = ma = m(0) = 0 Feb 26, 2015 #4 BvU

Frictional force is horizontal, pulling is in some theta direction. What else ? (hint: you already wrote mg -- and there's no vertical acceleration either). So we have a few equations. Magnitude of pulling force might depend on theta. If so, there might be a minimum !

Feb 26, 2015 #5 Yam

Forces that play a role:

1) Pulling force F at an angle

2) Horizontal Frictional force

3) Weight of the block

Yes i understand that the magnitude of the puling force depends on theta, however, how do i relate it to the minimum force?

Feb 26, 2015 #6 BvU

One force missing still.

If |F| depends on theta like, say

then zero degrees would give a nice minimum, wouldn't it ?

Feb 26, 2015 #7 Yam

Is it the upward force generated by the pull at an angle?

Feb 26, 2015 #8 BvU

Wouldn't that mean that if you don't pull, the box drops down like a brick ?

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Introductory Physics Homework Help

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## Chapter 5 Physics Flashcards

Start studying Chapter 5 Physics. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

## Chapter 5 Physics

1) A 615 N student standing on a scale in an elevator notices that the scale reads 645 N. From this information, the student knows that the elevator must be moving

A) downward. B) upward.

C) You cannot tell if it is moving upward or downward.

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C

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Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P. The tension in the wire is T (see figure). Which one of the following relationships between T and P must be true?

A) T > P B) T = P C) P + T = 125 N D) P = T + 25 N E) P = T + 100 N

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D

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1/68 Created by nicolim

### Terms in this set (68)

1) A 615 N student standing on a scale in an elevator notices that the scale reads 645 N. From this information, the student knows that the elevator must be moving

A) downward. B) upward.

C) You cannot tell if it is moving upward or downward.

C

Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P. The tension in the wire is T (see figure). Which one of the following relationships between T and P must be true?

A) T > P B) T = P C) P + T = 125 N D) P = T + 25 N E) P = T + 100 N D

Two objects having masses m1 and m2 are connected to each other as shown in the figure and are released from rest. There is no friction on the table surface or in the pulley. The masses of the pulley and the string connecting the objects are completely negligible. What must be true about the tension T in the string just after the objects are released?

A) T = m2g B) T > m2g C) T < m2g D) T = m1g E) T > m1g C

6) Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be

A) zero.

B) less than F but not zero.

C) equal to F. D) greater than F. B

8) Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest.

A) It takes the lighter object 5 times longer to reach the bottom of the incline than the heavier object.

B) It takes the lighter object 10 times longer to reach the bottom of the incline than the heavier object.

C) It takes the heavier object 5 times longer to reach the bottom of the incline than the lighter object.

D) It takes the heavier object 10 times longer to reach the bottom of the incline than the lighter object.

E) The two objects reach the bottom of the incline at the same time.

E

9) A box slides down a frictionless plane inclined at an angle θ above the horizontal. The gravitational force on the box is directed

A) parallel to the plane in the same direction as the movement of the box.

B) parallel to the plane in the opposite direction as the movement of the box.

C) perpendicular to the plane.

D) vertically.

E) at an angle θ below the inclined plane.

D

10) A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point down the ramp.

A) True B) False B

11) A brick is resting on a rough incline as shown in the figure. The friction force acting on the brick, along the incline, is

A) zero.

B) equal to the weight of the brick.

C) greater than the weight of the brick.

D) less than the weight of the brick.

D

12) A woman is straining to lift a large crate, without success because it is too heavy. We denote the forces on the crate as follows: P is the upward force the woman exerts on the crate, C is the vertical contact force exerted on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the woman is trying unsuccessfully to lift the crate?

A) P + C = W B) P + C < W C) P + C > W D) P = C A

13) If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out because an outward force balances the pull of gravity on the water.

A) True B) False B

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### Verified questions

Source : quizlet.com

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James 9 day ago

Guys, does anyone know the answer?