1. a. Which has more potential energy, a 10-kg box on a shelf or a 5-kg box on a shelf that’s twice as high? Explain.

   b. Which has more kinetic energy, a 2000-kg car traveling down the road or a 1000-kg car traveling twice as fast? Explain.

2. If your friend pushes a lawnmower six times as far as you do while exerting one half as much force, which one of you does more work? How much more? Explain.

3. a. A car has a certain amount of kinetic energy when it’s moving at 40 mph. If it speeds up until it’s going at 80 mph (two times faster), how many times more kinetic energy does it have? Explain.

   b. If the stopping distance for the car at 40 mph was about 75 ft, what is the stopping distance when it’s going two times faster? (Assume the stopping force stays the same. Keep in mind that Work, which is force × distance, is equal to the change in kinetic energy.)

4. An apple hanging from a limb has potential energy relative to the ground because of its height. If it falls, what has become of this energy just before it hits the ground? What has become of this energy after it hits the ground? Explain.

5. A roller coaster car has a potential energy of 10,000 J (relative to the ground) at the top of a certain hill, where it’s almost motionless. Then it rolls down the track. Explain your answers to these questions, assuming friction and air resistance can be neglected.

   1. The bottom of the hill is right at ground level. When the car gets there, how much potential energy and how much kinetic energy will it have?

   2. The car goes up another hill which is 3/4 as high as the original hill. How much potential energy and kinetic energy will the car have at the top of this second hill?

   3. The car goes down the second hill, where once again the track reaches ground level. How much potential energy and kinetic energy will the car have there?

A 195 g block is pressed against a spring of force constant 1.55 kN/m until the block compresses the spring 10.0 cm. The spring rests at the bottom of a ramp inclined at 60.0° to the horizontal. Using energy considerations, determine how far up the incline (in m) the block moves from its initial position before it stops under the following conditions.

(a)

if the ramp exerts no friction force on the block

_______m

(b)

if the coefficient of kinetic friction is 0.420

________m

(c)

What If? If the ramp is 4.00 m long, what is the maximum coefficient of friction that would allow the block to reach the end of the ramp?

__________

A long horizontal wire carries a current of 48 A. A second wire, made of 2.7 mm diameter copper wire and parallel to the first, is kept in suspension magnetically 15 cm below. Determine the magnitude of the current in the lower wire. Determine the direction of the current in the lower wire. IS IT IN STABLE EQUILIBRIUM?

Consider an electron confined to an infinite well of width 2ao (Bohr radius). Compare its energy in its three lowest energy states to the three lowest energy states of the Bohr model of the hydrogen atom. Repeat for a proton confined to a well of width 2x10-15 m (a nucleus).

8. Summarize the case for why Pluto should not be considered a planet.

If an electron in an atom has orbital angular momentum with ml values limited by ±2, how many values of (a) Lorb,z and (b) μorb,z can the electron have? In terms of h, m, and e, what is the greatest allowed magnitude for (c) Lorb,z and (d) μorb,z? (e) What is the greatest allowed magnitude for the z component of the electron's net angular momentum (orbital plus spin)? (f) How many values (signs included) are allowed for the z component of its net angular momentum?

can you explain light and matter using physics. Discoveries made by light and matter etc..

A square loop of wire with sides of length 34 cm is in a uniform magnetic field perpendicular to its area.

Part A

If the field's strength is initially 110 mT and it decays to zero in 0.011 s , what is the magnitude of the average emf induced in the loop?

Part B

What would be the average emf if the sides of the loop were only 17 cm ?

Express your answer using two significant figures.

A blow-dryer and a vacuum cleaner each operate with a voltage of 120 V. The current rating of the blow-dryer is 9.2 A, while that of the vacuum cleaner is 5.9 A. Determine the power consumed by (a) the blow-dryer and (b) the vacuum cleaner. (c) Determine the ratio of the energy used by the blow-dryer in 18 minutes to the energy used by the vacuum cleaner in 56 minutes.

In an attempt to escape his island, Gilligan builds a raft and sets to sea. The wind shifts a great deal during the day, and he is blown along the following straight lines:

2.5 km 45° north of west; then
4.70 km 60° south of east; then
5.1 km straight east; then
7.2 km 55° south of west; and finally
2.8 km 10° north of east.

What is his final position relative to the island?
______ km
______ ° south of east

A refracting telescope with a lens whose diameter is 26.0cm is used to view a binary star system that emits light in the visible region.

What is the minimum angular separation of the two stars for them to be barely resolved?

If the binary star is a distance of 4.00

Why does the very thin region at the top of a soap bubble sometimes appear black?

1. It is too thin to reflect light. 2. Inverted light waves and non-inverted light waves reflecting from the two surfaces cancel each other. 3. Both reflected waves are inverted or else neither is inverted. 4. No light passes through them.5. The rest of the film creates a shadow that obscures the colors we would otherwise see.

As a city planner, you receive complaints from local residents about the safety of nearby roads and streets. One complaint concerns a stop sign at the corner of Pine Street and 1st Street. Residents complain that the speed limit in the area (55 mph) is too high to allow vehicles to stop in time. Under normal conditions this is not a problem, but when fog rolls in visibility can reduce to only 155 ft. Since fog is a common occurrence in this region, you decide to investigate. The state highway department states that the effective coefficient of friction between a rolling wheel and asphalt ranges between 0.689 and 0.770, whereas the effective coefficient of friction between a skidding (locked) wheel and asphalt ranges between 0.450 and 0.617. Vehicles of all types travel on the road, from small VW bugs weighing 1070 lb to large trucks weighing 8550 lb. Considering that some drivers will brake properly when slowing down and others will skid to stop, calculate the minimum and maximum braking distance needed to ensure that all vehicles traveling at the posted speed limit can stop before reaching the intersection. minimum braking distance: ft maximum braking distance: ft Given that the goal is to allow all vehicles to come safely to a stop before reaching the intersection, calculate the maximum desired speed limit. maximum speed limit: mph Which factors affect the soundness of your decision? Precipitation from the fog can lower the coefficients of friction. Newton's second law does not apply to this situation. Drivers cannot be expected to obey the posted speed limit. Reaction time of the drivers is not taken into account.