1)A coffee cup on the dashboard of a car slides forward on the dash when the driver decelerates from 42.7 km/hr to rest in 3.72s or less, but not if he decelerates in a longer time. What is the coefficient of static friction between the cup and the dash?
2)A chain consisting of five links, each of mass 0.180 kg, is lifted vertically with a constant acceleration of a = 2.2 m/s2. Find the magnitude of the force that link 3 exerts on link 2. What is the magnitude of the force F that must be exerted on the top link to achieve this acceleration?
3)A railroad flatcar is loaded with crates. The coefficient of static friction between the crates and the floor is 0.26. If the train is moving at 58.1 km/hr, in how short a distance can the train be stopped with a constant acceleration without causing the crates to slide?
4)A block is at rest on an inclined plane whose elevation can be varied. The coefficient of static friction is µs= 0.44, and the coefficient of kinetic friction is µk = 0.15. The angle of elevation ? is increased slowly from the horizontal. At what value of ? does the block begin to slide (in degrees)? What is the acceleration of the block?
5)A block of mass 5.6 kg is pulled along a horizontal frictionless floor by a cord that exerts a force of 48.0 N at an angle 26.8° above the horizontal. What is the magnitude of the acceleration of the block? What is the magnitude of the normal force exerted on the mass by the floor?
The expert examines five problems on velocity, acceleration and frictions. The force exerted on the top link to achieve acceleration is determined.