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23 Nov 2019

Learning Goal: To understand kinetic and static friction.

A block of mass M lies on a horizontal table. The coefficient ofstatic friction between the block and the table is us. Thecoefficient of kinetic friction is uk, with uk<us .
A.If the block is at rest (and the only forces acting on the blockare the force due to gravity and the normal force from the table),what is the magnitude of the force due to friction?

Part B
Suppose you want to move the block, but you want to push it withthe least force possible to get it moving. With what force F mustyou be pushing the block just before the block begins tomove?
Express the magnitude of in terms of some or all the variables f,us,uk, and m, as well as g the acceleration due to gravity .

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Tod Thiel
Tod ThielLv2
15 Jan 2019

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Related textbook solutions

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

Related questions

A block of mass m lies on a horizontal table. The coefficient of static friction between the block and the table is μs. The coefficient of kinetic friction is μk, with μk<μs.

Part A

If the block is at rest (and the only forces acting on the block are the force due to gravity and the normal force from the table), what is the magnitude of the force due to friction?

Part B

Suppose you want to move the block, but you want to push it with the least force possible to get it moving. With what force F must you be pushing the block just before the block begins to move?

Express the magnitude of F in terms of some or all the variables μs,μk, and m, as well as the acceleration due to gravity g.

Part C

Suppose you push horizontally with half the force needed to just make the block move. What is the magnitude of the friction force?

Express your answer in terms of some or all of the variables μs, μk, and m, as well as the acceleration due to gravity g.

Part D

Suppose you push horizontally with precisely enough force to make the block start to move, and you continue to apply the same amount of force even after it starts moving. Find the acceleration a of the block after it begins to move.

Express your answer in terms of some or all of the variables μs, μk, and m, as well as the acceleration due to gravity g.

A 3.1 kg block is placed on top of a 8.22 kg block. A horizontal force of F = 55.5 N is applied to the 8.22 kg block, and the 3.1 kg block is tied to the wall. The coefficient of kinetic friction between all moving surfaces is 0.196. There is friction both between the masses and between the 8.22 kg block and the ground. The acceleration of gravity is 9.8m/s^2. Determine the magnitude of the acceleration of the 8.22 kg block. Answer in units of m/s^2.

Two blocks of masses ml and m2, are placed on a table in contact with each other as discussed in Example 5.7 and shown in Figure 5.13a. The coefficient of kinetic friction between the block of mass m1 and the table is pi., and that between the block of mass m2 and the table is g2. A horizontal force of magnitude Pis applied to the block of mass mi. We wish to find P, the magnitude of the contact force between the blocks. (a) Draw diagrams showing the forces for each block. (b) What is the net force on the system of two blocks? (c) What is the net force acting on mi? (d) What is the net force acting on m2? (e) Write Newton's second law in the x direction for each block. (f) Solve the two equations in two unknowns for the acceleration a of the blocks in terms of the masses, the applied force F, the coefficients of friction, and g. (g) Find the magnitude P of the contact force between the blocks in terms of the same quantities.

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