1) Greezy works in a factory because he does not make enough money from The Charming Beggars. He is pushing a very large crate of 50 kg across the floor at a constant velocity with a force of 200 N. He is pushing on the crate upwards at an angle of 20 °. See diagram.
(a) What is the coefficient of kinetic friction between the ground and the crate?
(b) Greezy increases his force to 400 N. What is the acceleration of the crate?
2) Two masses, m1 = 10 kg and m2 = 5 kg, are connected by a string that passes over a pulley as shown below. Mass #1 is on a frictional surface. The system is released from rest. After 1.2 s, mass #2 drops 1.0 m. Calculate the coefficient of kinetic friction between the surface and mass 111.
3) A large block of mass 25 kg is being accelerated along a frictionless surface by a horizontal force F. A smaller block of mass 4 kg is in contact with the front surface of the large block and will slide downward unless F is sufficiently large. The coefficient of static friction between the blocks is 0.71.
Calculate the smallest magnitude that F can have in order to keep the block from sliding downward.
4) Skid of mass 45 kg is in orbit around the planet Hctina in the solar system Sraggeb. Skid is traveling at 4.05 x 104 m/s. Hctim has a mass of 1.9 x 1027 kg and a radius of 7.14 x 107 m.
Calculate Skid's altitude above the surface of the planet.
5) An air puck of mass 0.25 kg is traveling in a circle of radius 1 m. The puck is attached to a cable that passes through a hole in a frictionless table. The other end of the cable is attached to a hanging weight of 1 kg. The air puck is moving in a circular path on the table so that the hanging weight will remain motionless. See diagram below.
(a) Find the tension in the cable,
(b) Name the force that is causing the air puck to move in a circle.
(c) What is the velocity of the puck?
6) At Magic Mountain there is a ride in which people stand up against the inside wall of a large cylinder of radius 3 in. The cylinder is then spun with a velocity of 15 m/s at which point the floor drops away leaving the riders suspended against the wall.
What is the minimum coefficient of static friction between the rider's clothing and the wall in order to keep the rider from sliding down?
7) A mass is hung from a ceiling by a cable that is 2 m in length. The mass is swung around so that it travels in a horizontal circle. While swinging the cable makes an angle of 30° with the vertical.
Find the velocity of the mass in order to maintain the angle.
8) A horizontal spring with a mass of 8 kg is pulled out to a distance of 15 cm with an external force of 200 N. If the mass is released (i.e. no more external force) from this point, what will be its acceleration when it is 10 cm from equilibrium?
1) a) 0.445 b) 4.38 m/s2
2) 0.288
3) 400 N
4) 5.9 x 106m
5) a) 9.8 N c) 6.26 m/s
6) 0.131
7) 2.38 res
8) 16.7 m/s2