Crn 10550, 15488, MWF 1:10 - 2:00 pm, Spring 2012
Homework 5
Assigned 2/21/12, Due 2/27/12
1. A very steep road has a slope of 5.19 degrees. What force is required to move a 20 ton object at constant speed along the road? Ignore friction.
2. An elevator consists of pulley, counterweight, and elevator cage. The counterweight is 2200 lb and the elevator is 2000 lb. (a) What is the upward acceleration of the elevator cage if the pulley runs freely? (b) What are the tensions in the cable if the pulley is locked( braked) so that the elevator doesn't move?
3. Two blocks, m1 and m2, are in contact on a horizontal table (m1 to the left of m2). A horizontal force, F, is applied to the left of block m1. If m1 = 2kg, m2 = 1kg, and F =3N, find the force of contact between the two blocks.
4. A block is slid down a 5 degree incline with the horizontal. The coefficient between the bottom of the block and the surface is .08. What is the acceleration of the block?
5. What is the weight of a 74 kg man? What is his weight in pounds?
6. A woman pulls the string of a bow (bow and arrow) with her hand with a force of 40 lb. If the two halves of the string above and below her hand make an angle of 120 degrees with each other, what is the tension in each half of the string?
7. A train has a total mass of 16,000 tons. The locomotive exerts a pull of 670,000 N on the train. What is the acceleration? How long does it take to increase the speed from 0 to 50 km/h?
8. A 45 degree wedge is pushed along a table with constant acceleration A. A block of mass m slides without friction on the wedge. Find its acceleration.
9. A block rests on a wedge inclined at an angle theta. The coefficient of friction between the clock and plane is mu. (a) Find the maximum value of theta fro the block to remain motionless on the wedge when the wedge is fixed in position. (b)The wedge is given horizontal acceleration a. Assuming that tan(theta) < mu, find the minimum acceleration for the block to remain on the wedge without sliding.