1. Give two everyday examples of objects that are not in static equilibrium.
2. Give two everyday examples of objects that are in static equilibrium.
3. Suppose the person climbs higher on the ladder. As a result, is the ladder more likely, less likely, or equally likely to slip? Explain.
4. A person holds a 1.42N baseball in his hand, a distance of 34.0cm from the elbow joint, as shown in figure 11-28 (please see the attachment). The biceps, attached at a distance of 2.75 from the elbow, exerts an upward force of 12.6N on the forearm. Consider the forearm and hand to be a uniform rod with a mass of 1.20 kg.
(a) Calculate the net torque acting on the forearm and hand. Use the elbow joint as the axis of rotation.
(b) If the net torque obtained in part (a) is nonzero, in which direction will the forearm and hand rotate?
(c) Would the torque exerted on the forearm by the biceps increase or decrease if the biceps were attached farther from the elbow joint?
5. Referring to the person holding a baseball in problem 4, suppose the biceps exert just enough upward force to keep the system in static equilibrium.
(a) Is the force exerted by the biceps more than, less than, or equal to the combined weight of the forearm, hand, and baseball? Explain.
(b) Determine the force exerted by the biceps.
6. A 0.11 kg meter stick is held perpendicular to a vertical wall by a 2.5m string going from the wall to the far end of the stick.
(a) Find the tension in the string.
(b) If a shorter string is used, will its tension be greater than, less than, or the same as that found in part (a)
(c) Find the tension in 2.0 m string.
7. A hand help shopping basket 62.0 cm long has a 1.81 kg carton of milk at one end, and a 0.722 kg box of cereal at the other end. Where should a 1.80 kg container of orange juice be placed so that the basket balances at its center?
8. Two different objects receive different amounts of heat but experience the same increase in temperature. Give at least two possible reasons for this behavior.
9. Two different objects receive the same amount of heat. Give at least two reasons why their temperature changes may not be the same.
10. The specific heat of concrete is greater that of soil. Given this fact, would you expect a major league baseball field or the parking lot that surrounds it to cool off more in the evening following a sunny day?
11. Two objects are made of the same material but have different temperatures. Object 1 has a mass m, and object 2 has a mass 2m. If the objects are brought into thermal contact, is the temperature change of object 1 greater than, less than, or equal to the temperature change of object 2? Explain.
12. A certain amount of heat is transferred to 2 kg og aluminum, and the same amount of heat is transferred to 1 kg of ice. Referring to table is the increase in temperature of the aluminum greater than, less than, or equal to the increase in temperature of ice? Explain.
| 212 |
100 |
373 |
| 32 |
0 |
273 |
| 109 |
78 |
195 |
| 321 |
196 |
77 |
| 460 |
273 |
0 |
13. More than likely, there is a glowing incandescent light bulb in your room at this moment. The filament of that bulb, with a temperature of about 4500 degrees F, is almost half as hot as the surface of the sun. What is this temperature in degrees Celsius?
14. Suppose 69.3 J of heat is added to a 121g piece of aluminum at 22.5 degrees C. What is the final temperature of the aluminum?
15. How much heat is required to raise the temperature of a 55 g glass ball by 15C.
16. A 5.0 lead bullet is fired into a fence post. The initial speed of the bullet is 250m/s, and when it comes to rest, half its kinetic energy goes into heating the bullet. How much does the bullet's temperature increase?
17. To determine a a specific heat on an object, a student heats it 100 degrees C in boiling water. She then places the 38.0 g object in a 155g aluminum calorimeter containing 103g of water. The aluminum and water are initially at a temperature of 20.0 degrees C, and are thermally insulated from their surroundings. If the final temperature is 22.0 degrees C, what is the specific heat of the object? Referring to above table identify the material in the object?