1. [-/2 Points] DETAILS OSCOLPHYS2016 5.1.P.002. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) When rebuilding her car's engine, a physics major must exert 110 N of force to insert a dry steel piston into a steel cylinder. What is the magnitude of the normal force in newtons between the piston and cylinder? (b) What is the magnitude of the force in newtons she would have to exert if the steel parts were oiled? Additional Materials Reading 2. [-/2 Points] DETAILS OSCOLPHYS2016 5.1.P.003. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) What is the maximum frictional force (in N) in the knee joint of a person who supports 77.0 kg of her mass on that knee? N (b) During strenuous exercise it is possible to exert forces to the joints that are easily ten times greater than the weight being supported. What is the maximum force of friction (in N) under such conditions? (The frictional forces in joints are relatively small in all circumstances except when the joints deteriorate, such as from injury or arthritis. Increased frictional forces can cause further damage and pain.) N3. [-/4 Points] DETAILS OSCOLPHYS2016 5.1.P.005. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) If half of the weight of a flatbed truck is supported by its two drive wheels, what is the maximum acceleration (in m/s ) it can achieve on wet concrete where the coefficient of kinetic friction is 0.5 and the coefficient of static friction is 0.7. m/s2 (b) Will a metal cabinet lying on the wooden bed of the truck slip if it accelerates at this rate where the coefficient of kinetic friction is 0.3 and the coefficient of static friction is 0.55? O No O Yes (c) If the truck has four-wheel drive, and the cabinet is wooden, what is it's maximum acceleration (in m/s-)? m/s2 Will it slip? O No O Yes4. [-/4 Points] DETAILS OSCOLPHYS2016 5.1.P.006. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A team of eight dogs pulls a sled with waxed wood runners on wet snow (mush!). The dogs have average masses of 19.5 kg, and the loaded sled with its rider has a mass of 205 kg. (a) Calculate the magnitude of the acceleration (in m/s*) starting from rest if each dog exerts an average force of 150 N backward on the snow. m / s2 (b) What is the magnitude of the acceleration (in m/s*) once the sled starts to move? |m/s2 (c) For both situations, calculate the magnitude of the force (in N) in the coupling between the dogs and the sled. Fpart (a) N Fpart (b) Additional Materials Reading 5. [-/3 Points] DETAILS OSCOLPHYS2016 5.1.P.013. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Calculate the maximum deceleration (in m/s*) of a car that is heading down a 90 slope (one that makes an angle of 90 with the horizontal) under the following road conditions. You may assume that the weight of the car is evenly distributed on all four tires and that the static coefficient of friction is involved-that is, the tires are not allowed to slip during the deceleration. (a) on dry concrete m/s2 (b) on wet concrete m/s2 (c) on ice, assuming that U = 0.100, the same as for shoes on ice m/s26. [-/2 Points] DETAILS OSCOLPHYS2016 5.1.P.016. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A freight train consists of two 7.00 x 10* kg engines and 42 cars with average masses of 5.00 x 10* kg. (a) What force (in N) must each engine exert backward on the track to accelerate the train at a rate of 6.00 x 1072 m/s if the force of friction is 7.50 x 10 N, assuming the engines exert identical forces? This is not a large frictional force for such a massive system. Rolling friction for trains is small, and consequently trains are very energy-efficient transportation systems. (Enter the magnitude.) N (b) What is the magnitude of the force (in N) in the coupling between the 37 and 38" cars (this is the force each exerts on the other), assuming all cars have the same mass and that friction is evenly distributed among all of the cars and engines? (Assume both engines are at the front of the train.)7. [-/3 Points] DETAILS OSCOLPHYS2016 5.1.P.017. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Consider the 68.0 kg mountain climber in the figure. 31 Flegs 150 (a) Find the tension in the rope (in N) and the force that the mountain climber must exert with her feet (in N) on the vertical rock face to remain stationary. Assume that the force is exerted parallel to her legs. Also, assume negligible force exerted by her arms. tension in rope N force on feet N (b) What is the minimum coefficient of friction between her shoes and the cliff?8. [-/3 Points] DETAILS OSCOLPHYS2016 5.1.WA.002. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER You are helping your friend move a new refrigerator into his kitchen. You apply a horizontal force of 259 N in the positive x direction to try and move the 63 kg refrigerator. The coefficient of static friction is 0.57. (a) How much static frictional force does the floor exert on the refrigerator? Give both magnitude (in N) and direction. magnitude N direction ---Select--- v (b) What maximum force (in N) do you need to apply before the refrigerator starts to move? N Additional Materials Reading 9. [-/2 Points] DETAILS OSCOLPHYS2016 5.1.WA.004. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Mary applies a force of 79 N to push a box with an acceleration of 0.58 m/s. When she increases the pushing force to 90 N, the box's acceleration changes to 0.78 m/s. There is a constant friction force present between the floor and the box. (a) What is the mass of the box in kilograms? kg (b) What is the coefficient of kinetic friction between the floor and the box?ASK YOUR TEACHER PRACTICE ANOTHER Alex is asked to move two boxes of books in contact with each other and resting on a rough floor. He decides to move them at the same time by pushing on box A with a horizontal pushing force FP : 8.9 N. Here 10. [-13 Points] OSCOLPHYSZEHB 5.1.WA.012.TUTORIAL. a a A has a mass {NA = 11.0 kg and B has a mass mE = 71) kg The contact force between the two boxes is FC. The coefficient of kinetic friction between the boxes and the floor is 0'02. (Assume Fp acts in the +x direction) (a) What is the magnitude (in mfsz) of the acceleration of the two boxes? |:| m? (b) What is the force exerted on mB by mA? In other words what is the magnitude (in N) of the contact force FCT' |:| N (c) If Alex were to push from the other side on the Ito-kg box, what would the new magnitude (in N) of EC be? :N 11. [-/5 Points] DETAILS OSCOLPHYS2016 5.1.WA.013. MY NOTES ASK YOUR TEACHER A block m, rests on a frictionless surface. A second block m, sits on top of the first block. Here m, = my = m. A horizontal force Fis applied to the bottom block to pull it to the right as shown below. Assume that the blocks move together across the surface (block m, does not slide off of block m, ). m2 (a) What is the magnitude of the acceleration of the blocks? (Use the following as necessary: m, g, and F.) (b) What are the magnitude and direction of the static friction force acting on m, due to my? (Use the following as necessary: m, g, and F.) magnitude f = direction ---Select--- v (c) What are the magnitude and direction of the static friction force acting on my due to my ? (Use the following as necessary: m, g, and F.) magnitude f = direction ---Select--- v