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(a) What is the maximum frictional force in the knee joint of a person who supports 66.0 kg of her mass on that knee? (b) During strenuous exercise it is possible to exert forces to the joints that are easily ten times greater than the weight being supported. What is the maximum
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- The coefficient of kinetic friction between a box and the floor is μk = 0.14 and the coefficient of static friction is μs = 2.0μk. Calculate the ratio of static to kinetic friction force if m = 8 kg.arrow_forwardA small box is held in place against a rough wall by someone pushing on it with a force directed upward at an angle of 260 above the horizontal. The coefficient of static and kinetic friction between the box and the wall are 0.40 and 0.30, respectively. The box slides down unless the applied force has a magnitude of 13 N. What is the mass of the box?arrow_forwardA 3.7 kg book is pressed against a wall with a force P at an angle of 35 degrees above the horizontal. The coefficient of static friction between the book and the wall is 0.75. (a)What is the minimum value of the force P that can hold the book to the wall (without it sliding down)? (b)If the force is applied at an angle of 35 degrees below the horizontal, what is the minimum value of the force P that can hold the book to the wall?arrow_forward
- A 22-kg crate is on an incline that makes an angle of 30° with the horizontal. If the coefficient of static friction is 0.50, the minimum force that can be applied parallel to the plane to hold the crate at rest is:arrow_forwardA 50-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the surface is 0.40, and the coefficient of kinetic friction is 0.30. What is the force of friction on the box?arrow_forwardDue to a jaw injury, a patient must wear a strap that produces a net upward force of 5.00 N on his chin. The tension is the same throughout the strap. To what tension must the strap be adjusted to provide the necessary upward force?arrow_forward
- A tool box of weighing 50.0 N rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.40, and the coefficient of kinetic friction is 0.20. If no horizontal force is applied to the box and the box is at rest, how large is the friction force exerted on the box?arrow_forwardIn the figure, a block weighing 23.0 N is held at rest against a vertical wall by a horizontal force of magnitude 61 N. The coefficient of static friction between the wall and the block is 0.55, and the coefficient of kinetic friction between them is 0.38. In six experiments, a second force P is applied to the block and directed parallel to the wall with these magnitudes and directions: (a)35 N, up, (b) 13 N, up, (c)48 N, up, (d)62 N, up, (e)9.1 N, down, and (f)19 N, down. In each experiment, what is the frictional force on the block, including sign? Take the direction up the wall as positive, and down the wall as negative. Next, calculate the acceleration, including sign, of the block in each case. Note that acceleration is zero if the block does not move. (g) What is the acceleration in (a)? (h) What is the acceleration in (b)? (i) What is the acceleration in (c)? (i) What is the acceleration in (d)? (k) What is the acceleration in (e)? (1) What is the acceleration in (f)?arrow_forwardA rope exerts a force of 50 N on a box to keep it stationary. If the box is on a plane inclined 25° from the horizontal and the coefficient of static friction is 0.29, calculate the normal force exerted on the box.arrow_forward
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