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Properties of Friction ,

IE. A bedroom bureau with a mass of 45 kg, including drawers and clothing, rests on the floor. (a) If the coefficient of static friction  between the bureau and the floor is 0.45, what is the magnitude of the minimum horizontal force that a person must apply to start the bureau moving? (b) If the drawers and-clothing, with 17 kg mass, are removed before the bureau is pushed, what is the new minimum magnitude?

2E. The coefficient of static friction between Teflon and scrambled eggs is about 0.04. What is the smallest angle from the horizontal that will cause the eggs to slide across the bottom of a coated skillet?

3E. A baseball player with mass m = 79 kg, sliding into second base, is retarded by a frictional force of magnitude 470 N. What is the coefficient of kinetic friction 14 between the player and the ground?

4E. The mysterious sliding stones. Along the remote Racetrack Plays in Death Valley, California, stones sometimes gouge out prominent trails in the desert floor, as if they had been migrating . For years curiosity mounted about why the stones moved.


5E. A person pushes horizontally with a force of 220 N on a 55 kg crate to move it across a level floor. The coefficient of kinetic friction is 0.35. (a) What is the magnitude of the frictional force?

6E. A house is built on the top of a hill with a nearby 45° slope(Fig. 6-19). An engineering study indicates that the slope angle should be reduced because the top layers of soil along the slope  might slip past the lower layers.


7E. A 110 g hockey puck sent sliding over ice is stopped in 15 m by the frictional force on it from the ice. (a) If its initial speed is 6.0 min, what is the magnitude of the frictional force? (b) What is the coefficient of friction between the puck and the ice?

8E. In a 49 kg rock climber is climbing a chimney between two rock slabs.

9P. A 12 N horizontal force F pushes a block weighing 5.0 N against a vertical wall.


1OP. A 2.5 kg block is initially at rest on a horizontal surface. A 6.0 N horizontal force and a vertical force P are applied to the block.

11P. A worker wishes to pile a cone of sand onto a ‘circular area in his yard. The radius of the circle is R. and no sand is to spill onto the surrounding area is the static coefficient friction between each layer of sand along the slope and the sand beneath it (along which it might slip).


12P.  The least pull that will get the crate moving crate is dragged across a floor by pulling on a rope attached to the crate and inclined 15° above the  the coefficient of static friction.

13P. A worker pushes horizontally on a 35 kg crate with ‘a force of magnitude 110 N. The coefficient of static friction between the crate and the floor is 0.37.

14P. A slide-loving pig slides down a certain 35° slide  in twice the time it would take to slide down a friction less 35° slide.


15P. A block is pushed along’ a horizontal floor by a force 0f magnitude 15 N at an angle , (J = 40° with the horizontal . The coefficient of kinetic.


16P Shows the cross section of road cut into the side of a mountain. The solid line represents a weak bedding plane ‘)l along which sliding is possible.


l7P. A loaded penguin sled weighing 80 N rests on a plane inclined at 20° to the horizontal (Fig. 6-28). Between the sled and the plane, the coefficient of static friction is 0.25. and the coefficient of kinetic friction is 0.15.


18P. Block B in  weighs 711 N. The coefficient of static friction between block.


19P.Body A weighs 102 N, and body B weighs 32 N. The coefficients of friction between A and the incline. Find the acceleration of A if (a) A is. initially at rest.

20P. In  two blocks are connected over a pulley. The mass of block A is 10 kg and the coefficient of kinetic friction between A and the incline is 0.20.


21P. Two blocks, of weights 3.6 N and 7.2 N, are connected by a mass less string and slide down a 30· inclined plane. The coefficient of kinetic friction between the lighter block and the plane is 0.10.

22P.In  a box of Cheers and a box of Wheaties are accelerated across a horizontal surface  by a horizontal force F applied to the Cheerios box.


24P.The two blocks  shown in  are not attached. The coefficient of static friction between the blocks but the surface beneath the larger block is friction less.

25P. A 40 kg slab rests on a friction less floor. A 10 kg block rests on top of the slab. The coefficient of static friction between the block and the slab is 0.60.

26p. A locomotive accelerates a 25-car train along a level track. Every car has a mass of 5-.0 X 104 kg and is subject to a frictional force.

28P. A crate slides down an inclined right-angled trough. The coefficient of kinetic friction between the crate .

29P. An initially stationary box of sand is to be pulled across a floor by means of a cable in which the tension should not exceed.

30P. A high-speed railway car goes around a flat, horizontal circle of radius 470 m at a constant speed.

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