Physics

Test Your Physics Knowledge:

Yes/No
1. In steady flow, the velocity v of a fluid particle at any point is constant in time. On the other hand, the fluid in a pipe accelerates when it moves from a larger-diameter section of the pipe into a smaller-diameter section, so the velocity is increasing during the transition. Does the condition of steady flow rule out such an acceleration?
2. Suppose that you stand in front of a spherical mirror (concave or convex). Is it possible for your image to be (a) real and upright (b) virtual and inverted?
3. Is the acceleration of a projectile equal to zero when the projectile reaches the top of its trajectory?
4. On a distant asteroid, a large catapult is used to throw chucks of stone into space. Could such a device be used as a propulsion system to move the asteroid closer to the earth?

Physics Problems
1. The corners of a square lie on a circle of diameter D = 0.35 m. Each side of the square has a length L. Find L.
2. The temperatures indoors and outdoors are 299 and 312 K, respectively. A Carnot air conditioner deposits 6.12 x 105 J of heat outdoors. How much heat is removed from the house?

Multiple Choice
1. A net external nonconservative force does positive work on a particle. Based solely on this information, you are justified in reaching only one of the following conclusions. Which one is it?
1. The kinetic and potential energies of the particle both decrease
2. The kinetic and potential energies of the particle both increase
3. Neither the kinetic nor the potential energy of the particle changes
4. The total mechanical energy of the particle decreases
5. The total mechanical energy of the particle increases
2. Is it possible for the temperature of a substance to rise without heat flowing into the substance?
1. Yes, provided that the volume of the substance does not change
2. Yes, provided that the substance expands and does positive work
3. Yes, provided that work is done on the substance and it contracts
3. Which of the following statements can be explained by Newton’s forst law? (A): When your car suddenly comes to a halt, you lunge forward. (B): When your car rapidly accelerates, you are pressed backward against the seat.
1. Neither A nor B
2. Both A and B
3. A but not B
4. B but not A
4. The transfer of heat by convection is smallest in __________.
1. Solids
2. Liquids
3. Gasses
5. One day during the winter the sun has been shining all day. Toward sunset a light snow begins to fall. It collects without melting on a cement playground, but melts instantly on contact with a black asphalt road adjacent to the playground. Why the difference?
1. Being black, asphalt has a higher emissivity than cement, so the asphalt absorbs more radiant energy from the sun during the day and, consequently, warms about the freezing point.
2. Being black, asphalt has a lower emissivity than cement, so the asphalt absorbs more radiant energy from the sun during the day and, consequently, warms about the freezing point.

Answers:

Yes/No
1. No
2. a. No - b. No
3. No
4. Yes

Physics Problems
1. 0.25 m
2. 5.86 x 105 J

Multiple Choice
1. e
2. c
3. b
4. a
5. a