HW#14 Ch 5: Force and Motion — I
Instructions: Show all work using Newton’s 2nd law and free body diagrams.
1. Brimming with pride, a recent Moravian Academy graduate hangs a 4.7 kg picture of the school on his wall. Eschewing all notions of symmetry, she hangs the picture using two unequal pieces of cord from two nails in the wall, labeled A and B (see associated figure). If the angle that cord A makes with the horizontal is 32° and the angle that cord B makes with the horizontal is 65°, what are the tensions in cords A and B?
2. A 4.5 kg block hangs from a cord, which is looped over a second cord, having one end attached to the ceiling and a second end looped over a pulley. An unknown weight hangs from the end of the second cord. If the system is in equilibrium, and the second cord forms an angle of 30° with respect to the vertical (as shown in the associated figure), what are the tensions T1, T2 and T3, and what is the unknown mass m?
3. A ballerina pulls a 12 kg crate of apples up a frictionless ramp at constant velocity (see attached figure). If the ramp has an angle of 23° with respect to the horizontal, a) what is the normal force on the ramp? b) With what force does the ballerina pull on the rope?
4. You apply a horizontal force of 60 N to a 7 kg block, which causes it to accelerate up a frictionless ramp that is inclined at 20°. a) What is the normal force of the block? b) What is the magnitude of the acceleration of the block?