VIEWS: 89 PAGES: 3 POSTED ON: 3/24/2011
AP Physics Name: Lessons 9 and 10 Homework Torque and Universal Date: Gravitation 1. A uniform meterstick pivoted at its center has a 100g mass suspended at the 25.0 cm position. (a) At what position should a 75.0g mass be placed to put the system in equilibrium? (b) What mass would have to be placed at the 90.0cm position for the system to be in equilibrium? 2. The pedals of a bicycle rotate in a circle with a diameter of 40 cm. What is the maximum torque a 55kg rider can apply by putting all of her weight on one pedal? 3. A 20kg ladder of 3.0m length is placed at a 80o angle against a wall. What is the frictional force that has to act on the bottom of the ladder to keep it from slipping? 4. A painter of 75kg mass is standing on a rung two thirds up from the bottom of the ladder that was described in 2. How much friction has to act on the bottom of the ladder to keep it from slipping? 5. Telephone and electrical lines are allowed to sag between the poles so that the tension will not be too great when something hits or sits on the line. (a) Is it possible for the lines to be perfectly horizontal? Justify your answer. (b) Suppose that the lines would sag only 0.10 m exactly halfway between the poles that are 30 m apart. If a 0.25 kg bird sits on the wire midway between the poles and you would ignore the mass of the wire itself, what would be the tension in the wire? 6. What is the acceleration due to gravity on top of Mt. Everest? The summit is about 8.80 km above sea level. 7. For a spacecraft going directly from the Earth to the Moon, beyond what point will lunar gravity dominate? Are the astronauts onboard a spacecraft at this point truly weightless? 8. Two inquisitive physics students arranged for a high jump competition at the summit of Mt. Everest. At sea level they are able to elevate their center of gravity 1.20 m during a high jump. How much elevation would their center of gravity experience on Mt. Everest. Neglect differences in air density and the additional gear they might have to wear. 9. Two objects are attracting each other with a certain gravitational force. (a) How would the force between the objects change if they were placed at a distance 3 times the original? (b) How would you have to change the masses to keep the gravitational force the same as the original. 10. A 75 kg man weighs 735N on the surface of Earth. How far above the surface of the Earth would he have to go to “lose” 10% of his body weight? 11. Four identical masses of 2.5 kg each are located at the corners of a square with 1.0 m sides. What is the net force on any one of the masses? Where would the net gravitational force be zero?
Pages to are hidden for
"AP Physics Lessons and Homework Torque and Universal"Please download to view full document