71. A man stacks a small block of wood on top of a larger block and then moves both by pushing the bottom block. The large block has a mass of 25 kg, and the smaller block has a mass of 15 kg. The coefficient of static friction between the two blocks is 0.45. How fast can the man accelerate the blocks without having the smaller block slide off the top? (4.2, 4.3) T/I

A man is trying to move an object (m 14.0 kg) by pulling upward on the rope at an angle of 53° above the horizontal. The coefficient of kinetic friction is 0.300 between the object and the ground. The tension in the rope is 150 N. What is the acceleration of the object? 53 O 6.08 m/s2 O 6.86 m/s2 O 3.50 m/s2 7.77 m/s2 6.82 m/s2

A 2kg box is given a swift kick, and then allowed to slide along the ground until friction slows it to a stop. If the coefficient of static friction between this box and the ground is 0.7, and the coefficient of kinetic friction is 0.5, what is the magnitude of the acceleration that this box will experience? *   4.9 m/s/s 2.7 m/s/s 6.3 m/s/s 9.8 m/s/s

16. Running without friction is impossible. In fact, to maximize your acceleration, you need to maximize the static friction between your shoes and the floor. a) Explain why static friction is necessary for running or walking. requirement, employees' shoes must have a coefficient of static friction of 0.5 or more on a specified tile surface. In an emergency, what is the minimum time interval in which a postal worker starting from rest can move a distance of 3 m on the tile surface? c) A typical athletic shoe has a coefficient of static friction of 0.8 when used on a running track. What is the minimum time interval in which an athlete starting from rest can move a distance of 100 m on a running track? b) To meet a U.S. Postal Service

9. A 100 kg man gets in an elevator on the 10th floor. He stands still on a scale, which is placed on the floor of the elevator, before the doors close, and the scale reads a value equal to his weight (the largest force of gravity on him). The doors close, and the elevator starts moving downward toward the 1st floor. The elevator speeds up until it reaches the 8th floor, at which point the elevator travels at a constant velocity, which it maintains until it reaches the 3rd floor, at which point it starts slowing down at a constant rate and stops by the time it reaches the 1st floor. Rank from greatest to least, the following quantities at following floors: 2nd, 5th, 9th. Explain your answers. (a) His mass (the question is asking for a ranking of the person's mass on the 2nd floor vs. the mass on the 5th floor vs. the mass on the 9th floor.) (b) His weight (c) Magnitude of normal force he exerts on the scale (d) Magnitude of normal force he exerts on the elevator floor.

A wooden box of mass 30 kg slides on a concrete floor. What is the coefficient of friction if the frictional force acting between the box and the surface is 180 N? 0.061 0.312 0.031 O 0.612

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall. The block is initially at rest. If µ. – 0.60 and 0.50, the acceleration of the block is: Ⓒ4.8 m/s² Ⓒ3.8 m/s² Ⓒ 9.8 m/s² 0.0 m/s² 08.0 m/s2

2.8 kg object. What is the value of ax the x-component of the object's acceleration?

The tension at which a fishing line snaps is commonly called the line's "strength." What minimum strength is needed for a line that is to stop a salmon of weight 92 N in 12 cm if the fish is initially drifting horizontally at 2.7 m/s? Assume a constant deceleration. Number i Units

A crate of mass 38.6 kg rests on a level surface, with a coefficient of kinetic friction 0.258. You push on the crate with an applied force of 219 N. What is the magnitude of the crate s acceleration as it slides?   A 6.80 m/s^2   B 3.14 m/s^2   C 5.67 m/s^2   D 2.51 m/s^2