Physics 151 - Homework #5 - 14 points possible Instructions: Write your full solutions on separate paper, then scan and upload them in the submission area on Blackboard by the due date listed there. You must show all work to receive credit unless otherwise indicated, Be sure to label all problem numbers and circle your answers. 1. (2 pts) Suppose you have a 120 kg wooden crate resting on a wood floor (coefficients of static and kinetic friction are given by 0.5 and 0.3 respectively). (a) What maximum force can you exert horizontally on the crate without moving it? (b) If you continue to exert this force once the crate starts to slip, what will the magnitude of its acceleration then be? 2. (1 pt.) The board sandwiched between two other boards in the figure weighs 95.5 N. If the coefficient of static friction between the boards is 0.665, what must be the magnitude of the compression force (assumed to be horizontal) acting on both sides of the center board to keep it from slipping? 3. (3 pts) A 68.0 kg snowboarder starts coasting up a snow-covered hill with an initial velocity of 8.80 m/s. The hill is angled at 25.0 above the horizontal, and the snowboarder comes to a rest after traveling 7.50 meters up the hill. (a) What is the magnitude of their deceleration as they coast to a stop? (Hint: you can use the kinematics equations for this part) (b) What is the magnitude of the friction force acting on them during their slow-down? (c) What is the coefficient of kinetic friction between the snowboard and the snow? 4. (1 pt) Semi-trailer trucks have an odometer on one hub of a trailer wheel. The hub is weighted so that it does not rotate, but it contains gears to count the number of wheel revolutions-it then calculates the distance traveled. If the wheel has a 1.15 m diameter and goes through 200,000 rotations, how many kilometers should the odometer read? 5. (2 pts) Earth rotates once on its axis every 24 hours. (a) What is the angular velocity of Earth? (b) Given that Earth has a radius of 6.4 x 10 m at its equator, what would be the tangential velocity of someone standing at the equator as measured by a "stationary" observer? 6. (1 pt) A rotating space station is said to create "artificial gravity"-a loosely-defined term used for an acceleration that would be crudely similar to gravity. The outer wall of the rotating space station would become a floor for the astronauts, and centripetal acceleration supplied by the floor would allow astronauts to exercise and maintain muscle and bone strength more naturally than in non-rotating space environments. If the space station is shaped like a tube, that is 200 m in diameter, what angular velocity would produce an "artificial gravity" of 9.80 m/s at the rim? 7. (1 pt) A coin rests 15.0 cm from the center of a turntable. The coefficient of static friction between the coin and the turntable surface is 0.350. The turntable starts from rest and begins increase its rate of rotation. At what angular velocity will the coin begin to slip? 8. (1 pt.) A 60.0 kg person swings on a 4.00 m long rope swing. The tension in the rope at the lowest point is 0.950 kN. Find the person's speed at the lowest point. Hint: draw a free-body diagram for this point in the motion, and note the direction of the centripetal acceleration. 9. (2 pts.) A roller coaster car has a mass of 500 kg when fully loaded with passengers. (a) If the car has a speed of 20.0 m/s 10 m 15 m at point A, what is the force of the track on the car at this point? (b) What is the maximum speed the vehicle can have at point B for it not to lose contact with the track
