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23 Nov 2019

A person is pulling a block of mass m w/ a force equal to itsweight directed 30 degrees above the horizontal plane across arough surface generating a friction f on the block. If the personis now pushing downward on the block with the same force 30 degreesabove the horizontal plane across the same rough surface what isthe friction on the block? Answer is 3f

Explanation states F=ukN where N is normal force acting on block. Iunderstand that however it then states when force is applied 30degrees above horizontal N=mg-mgsin30? How is that the normal forceI thought the normal was mgcos30? It the states when force isapplied 30 degrees below horizontal N=mg+mgsin30? Solving for N andplugging it into F=ukN and solving for uk gives 3f.

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

1. A block is placed on a plane whose angle of inclination is 30˚. The coefficients of static and kinetic friction for the block on the inclined plane are both 0.2. The block
(A) remains stationary on the inclined plane.
(B) accelerates down the inclined plane.
(C) travels down the inclined plane at a constant velocity.
(D) travels up the inclined plane at a constant velocity.
(E) accelerates up the inclined plane.

2. An object with a mass of 5.5 kg is allowed to slide from rest down an inclined plane. The plane makes an angle of 30˚ with the horizontal and is 72 m long. The coefficient of friction between the plane and the object is 0.35. The speed of the object at the bottom of the plane is?

3. A 5-kg object slides down a frictionless surface inclined at an angle of 30˚ from the horizontal. The total distance moved by the object along the plane is 10 meters. The work done on the object by the normal force of the surface is?

4. A mass m = 2.5 kg is sliding along a frictionless table with initial speed v as shown in the figure. It strikes a coiled spring that has a force constant k = 500 N/m and
compresses it a distance x=5.0 cm. The initial speed v of the block was..?



5. The graph shows how the position of a particle depends on time. Which choice is closest to the instantaneous speed of the particle at t = 3s?
(A) 0.40 m/s
(B) 0.67 m/s
(C) 0.75 m/s
(D) 1.50 m/s
(E) 2.22 m/s



6. Calculate the work done by a force, F = 2x i, along the
path (0, 0) -> P1(2, 0) -> P2(2, 2).



During a seventh-inning stretch of a baseball game,groundkeepers drag mats across the infield dirt to smooth it. Agroudskeeper is pulling a mat as a constant velocity by applying aforce of 120 N at at angle of 22 degrees above the horizontal. thecoefficient of kinetic friction between the mat and the ground is.60 Find the magnitude of the frictional force between the dirt andthe mat, and the weight and the mat.

Here I tried to find teh weight of the mat by adding all thex-components, which I had as Applied Force-FrictionalForce-x-component of MG+ the x-component of the Normal force.

I tried to find the Normal force by setting the x-components tozero and solving for N which gave me mg cos 22. to which Imultiplied the coefficient of kinetic friction. I tried to add allthe x-components together and solve for m and then multiply it by gto get the weight. I am obviously doing something wrong. Could youplease help me to solve this problem for weight and magnitude goingstep by step? I am studying for a test.

Thanks!

Please Help me How to solve this and explain pls, I'mreally bad at solving. Thank you

1) Resolve a force of 100N acting at an angle of 37degrees withthe horizontal into horizontal and vertical components.

2) An object weighing 40N rests on an inclined plane making anangle of 30 degrees with the horizontal. Resolve the force intocomponents parallel to the plane and perpendicular (normal) to theplane.

3) Resolve a force of 100N into two components which lie onopposite sides of the force and each of which makes an angleof 30 degrees with the force.

4) Two airplanes start from the same point, one traveling 250km Eand the other 180km N. What is the vector difference of these twodisplacements? What does it signify?

5) Three cities X, Y, and Z are connected by straight highways. Xis 6km from Y, Y is 4km from Z, and X is 5km from Z. Find the anglemade by the highways XY and YZ.

6) Four boxes each weighing 100N are suspended from a beam. What isthe tension in each of the wires.

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-> / 30 D \<- | | | \ <- 150 D -> /
~~~~~~~ ~~~~~~ ~~~~~~~~ |
| A | | B | | C | ~~~~~~~
~~~~~~~~ ~~~~~~~ ~~~~~~~~ | D |
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