UConn Physics 121 Final Exam Fall 2004
Instructions: You must choose 8 of the following 10 questions to do. You must indicate which problems you want graded. You may have your formula and conversion sheet and a calculator.
1. The 23 meter long log, shown above has a non-uniform mass distribution so that its center of gravity lies 16 m from its right hand end rather than the middle of the log. The log is supported from below at its right end by a triangular support. A cable is tied to the log 4 meters from its left end. The log weighs 7.5 x 103 N. Find the tension in the cable.
2.A 10 kg mass is on a, frictionless, 35 degree inclined plane as shown above. A second 20 kg mass is attached to the other end of the string and released. Assuming the pulley is frictionless and massless, what will be the speed of the 10 kg mass 0.1 sec after release?
3. A 900 kg car is moving on a horizontal road at 20 m/s when its brakes are applied. The car skids to a stop in 30 m. Find the coefficient of friction between the car’s tires and the road.
4.A 75 kg hockey player traveling at 12 m/s, collides with a 90 kg player traveling at right angles to the first at 15 m/s. If the players stick together, find the speed of the two players after the collision if momentum is conserved.
5.You eat 100 kcal worth of peanut butter cookies. How many meters high would you have to climb to “work off” those 100 kcal if your mass is 65 kg?
6.Assuming that the value of g at sea level is 9.81 m/s2, radius of earth is 6.37 x 106 m and the value of G is 6.67 x 10-11 Nm2/kg2, find the mass of the earth.
7. An iron cube is 4.47 cm on each edge. The cube is then dropped into a tank of water that is 20 m deep. Assuming the density of water is 1g/cm3 and atmospheric pressure is 1.01 x 105 Pa, what is the force due to the total pressure on one face of the cube?
8. A compass in an airplane indicates that it is headed due east. The speed of the plane relative to the air is 215 km/hr. A steady wind of 65 km/hr is blowing due north with respect to the ground. What is the magnitude of the velocity of the plane with respect to the ground?
9. A grindstone wheel as show, has a constant angular acceleration of 0.35 rad/s2. If it starts from rest, how many revolutions will it undergo after 18 seconds of this acceleration?
10. Someone kicks a soccer ball from ground level at a 30 degree angle with a velocity of 30m/s. Neglecting air resistance,
a. When the ball is halfway to its maximum vertical height above the ground, what is the magnitude and direction of the acceleration of the ball?
b. What is the total work done on the ball by the gravitational force during the total time the ball was in the air from point p to Q?