47. To meet a U.S. Postal Service requirement, employees' foot wear must have a coefficient of static friction of 0.500 or more on a specified tile surface. A typical athletic shoe has a coef ficient of 0.800. In an emergency, what is the minimum time interval in which a person starting from rest can move 3.00 m on the tile surface if she is wearing (a) footwear meeting the Postal Service minimum and (b) a typical athletic shoe? ~^^

You are designing a high-speed elevator for a new skyscraper. The elevator will have a mass limit of 2400 kg (including passengers). For passenger comfort, you choose the maximum ascent speed to be 18.0 m/s, the maximum descent speed to be 10.0 m/s, and the maximum acceleration magnitude to be 3.30 m/s2. Ignore friction. (a)What is the maximum upward force that the supporting cables exert on the elevator car? ___kN (b)What is the minimum upward force that the supporting cables exert on the elevator car? ____kN

A 60.0 kg crate rests on a level floor in a warehouse. The coefficients of static and kinetic friction are 0.850 and 0.550 respectively. (a) What horizontal pushing force is required to just start the crate to move across the floor? (b) What horizontal pushing force is required to keep the crate moving at a constant velocity across the floor? (c) Include a force (or free-body) diagram of each of the situations.

2 sig figs only

A toboggan approaches a snowy hill moving at 15.0 m/s. The coefficients of static and kinetic friction between the snow and the toboggan are 0.460 and 0.350, respectively, and the hill slopes upward at 41.0° above the horizontal. Find the acceleration of the toboggan as it is going up hill, and find the acceleration after it has reached the highest point and is sliding down hill.

A(n) 19_kg mass is on an incline, with a = 4.5_m and b = 2.3_m. The coefficient of kinetic friction between the mass and the surface of the incline is µg = 0.36. If the mass is initially near the top of the incline and sliding down, then what is the mass's acceleration down the incline? m b

A man is driving his car with speed 49.0 mi/h on a horizontal stretch of road. (a) When the road is wet, the coefficient of static friction between the road and the tires is 0.102. Find the minimum stopping distance (in m). m == (b) When the road is dry, H, = 0.598. Find the minimum stopping distance (in m). m

A block is placed on the midpoint of a ramp that is inclined at an angle of 39.8º from the horizontal, at which point the block immediately starts to slide down the ramp due to the fact that the static friction limit for this particular case is insufficient to hold the block in place. If the coefficient of kinetic friction between the block and the ramp is  0.277 , what is the magnitude of the acceleration of the block as it slides down the ramp.

10. To meet a U.S. Postal Service requirement, employees' footwear must have a coefficient of static friction of 0.5 or more on a specified tile surface. A typical athletic shoe has a coefficient of static friction of 0.800. In an emergency, what is the minimum time interval in which a person starting from rest can move 3.00 m on the tile surface if she is wearing (a) footwear meeting the Postal Service minimum and (b) a typical athletic shoe? Answers: a) 1.11 s b) 0.875 s