1. Which of the following energy transformations best describes the operation of a solar powered battery charger?

(a) electrical energy --> thermal energy --> kinetic energy
(b) nuclear energy --> potential energy --> chemical energy
(c) thermal energy --> elastic potential energy --> electrical energy
(d) radiant energy --> electrical energy --> chemical potential energy
(e) radiant energy --> thermal energy --> electrical energy

2. A jet engine applies a thrust force of 21.0 N vertically to a 0.500 kg rocket. The force of air friction is negligible for the first 50.0 cm of flight. Find the kinetic energy gained by the rocket in the first 50.0 cm of takeoff.
(a) 4.0 J
(b) 8.05 J
(c) 10.5 J
(d) 21 J
(e) 32 J

3. A 300 N force is applied horizontally to a 50kg crate, originally at rest, pushing it 2 m. The force of friction between the crate and the floor is 200 N. The final kinetic energy of the crate is:
(a)0 J
(b)200 J
(c)400 J
(d)600 J
(e)300000 J

4. The rated power output of an engine is 10 hp, 7460 W. How much energy would it produce in 10 minutes?
(a) 0 J
(b)100 J
(c) 74600 J
(d) 4.5 MJ
(e) 746 MJ

5. An electrical hair dryer consumes 90 kJ in one minute. What is the power used by this hair dryer?
(a) 90 W
(b) 100W
(c) 1500 W
(d) 5.4 kW
(e) 1 hp

1. (e) radiant energy --> thermal energy --> electrical energy. Or as some might say, "shining sunlight on it to charge it up!"

2. (a) 4.0 J. The rocket is off to a flying start!

3. (d) 600 J. That crate really got moving!

4. (e) 746 MJ. The engine's power knows no bounds!

5. (d) 5.4 kW. That hair dryer is blowing some serious power!

1. The correct answer is (e) radiant energy --> thermal energy --> electrical energy. A solar powered battery charger converts radiant energy from the sun into thermal energy, which is then converted into electrical energy to charge the battery.

2. To find the kinetic energy gained by the rocket, we can use the formula: Kinetic Energy = 1/2 * mass * velocity^2. Since the rocket is initially at rest, its initial velocity is 0 m/s. The thrust force acting on the rocket is equal to the net force, so we can use Newton's second law: F = mass * acceleration. Rearranging the equation, we get acceleration = F/mass. Plugging in the values, we have acceleration = 21.0 N / 0.500 kg = 42.0 m/s^2. Using the equation for displacement with constant acceleration, we have: displacement = (initial velocity * time) + (1/2 * acceleration * time^2). Plugging in the values, we have displacement = (0 m/s * 0.50 s) + (1/2 * 42.0 m/s^2 * (0.50 s)^2) = 5.25 m. Now, we can calculate the final velocity using the equation: final velocity = initial velocity + (acceleration * time). Plugging in the values, we have final velocity = 0 m/s + (42.0 m/s^2 * 0.50 s) = 21.0 m/s. Finally, we can calculate the kinetic energy using the formula: Kinetic Energy = 1/2 * mass * velocity^2 = 1/2 * 0.500 kg * (21.0 m/s)^2 = 4.0 J. Therefore, the correct answer is (a) 4.0 J.

3. The work done on an object is equal to the force applied multiplied by the distance traveled in the direction of the force. The work done on the crate is given by W = force * distance. Plugging in the values, we have W = 300 N * 2 m = 600 J. However, the force of friction is acting in the opposite direction of the applied force, so the work done by friction is W = force of friction * distance = 200 N * 2 m = 400 J (negative because it acts in the opposite direction). Therefore, the net work done on the crate is 600 J - 400 J = 200 J. The final kinetic energy of the crate is equal to the net work done on it because work done is equal to the change in kinetic energy. Therefore, the correct answer is (b) 200 J.

4. Power is defined as the rate at which energy is transferred or transformed. The formula for power is P = energy / time. Plugging in the values, we have P = 7460 W = energy / (10 minutes * 60 seconds/minute). Solving for energy, we have energy = P * time = 7460 W * (10 minutes * 60 seconds/minute) = 4,476,000 J = 4.5 MJ. Therefore, the correct answer is (d) 4.5 MJ.

5. Power is defined as the rate at which energy is transformed or transferred. The formula for power is P = energy / time. Plugging in the values, we have P = 90 kJ / (1 minute * 60 seconds/minute) = 1,500 W = 1.5 kW. Therefore, the correct answer is (e) 1.5 kW.

1. To determine the best energy transformation for a solar powered battery charger, we can analyze the process involved.

A solar powered battery charger converts radiant energy from the sun into electrical energy stored in the battery. Therefore, the correct energy transformation is (e) radiant energy --> thermal energy --> electrical energy.

Explanation: The sun emits radiant energy in the form of sunlight. The solar charger's photovoltaic cells absorb this radiant energy and convert it into thermal energy, through a process called the photovoltaic effect. The thermal energy is then used to generate electrical energy, which charges the battery.

2. To find the kinetic energy gained by the rocket in the first 50.0 cm of takeoff, we can use the formula for kinetic energy: KE = 1/2 * m * v^2.

In this problem, the thrust force applied is vertical, but the question asks about kinetic energy gained in the first 50.0 cm of flight, which is horizontal. Therefore, the vertical thrust force is not relevant here.

The kinetic energy gained is solely dependent on the change in velocity of the rocket. Since the force of air friction is negligible, we can assume that all the thrust force is used to accelerate the rocket horizontally.

First, we need to calculate the acceleration of the rocket:
F = m * a
21.0 N = 0.500 kg * a
a = 42.0 m/s^2

Next, we can calculate the final velocity (vf) using the kinematic equation:
vf^2 = vi^2 + 2 * a * d
0^2 + 2 * 42.0 m/s^2 * 0.500 m = vf^2
vf = 9.165 m/s

Finally, we can calculate the kinetic energy:
KE = 1/2 * m * v^2
KE = 1/2 * 0.500 kg * (9.165 m/s)^2
KE = 21.0 J

Therefore, the kinetic energy gained by the rocket in the first 50.0 cm of takeoff is (d) 21 J.

3. To find the final kinetic energy of the crate, we need to consider the work done on the crate by the applied force and the work done against friction.

The work done by the applied force can be calculated using the work formula: W = F * d * cos(theta), where F is the applied force, d is the displacement, and theta is the angle between the force and displacement vectors.

W_applied = 300 N * 2 m * cos(0 degrees) = 600 J

The work done against friction is given by the force of friction multiplied by the displacement:
W_friction = 200 N * 2 m = 400 J

The net work done on the crate is the sum of the work done by the applied force and the work done against friction:
Net work = W_applied - W_friction
Net work = 600 J - 400 J = 200 J

The work done on an object is equal to the change in kinetic energy, so the final kinetic energy of the crate is 200 J.

Therefore, the answer is (b) 200 J.

4. To calculate the energy produced by the engine in 10 minutes, we can multiply the power output of the engine by the time:

Energy = Power * Time

Here, the power output of the engine is given as 10 hp, which is equal to 7460 W.

Energy = 7460 W * 10 minutes

To perform the calculation, we need to convert the time from minutes to seconds, as the unit of power is in watts (Joules per second):

Energy = 7460 W * 10 minutes * (1 minute / 60 seconds)

Energy = 7460 W * 10 minutes * (1/60) s

Energy = 1243.33 J * 600 s

Energy = 746,000 J

Therefore, the engine would produce 746,000 J of energy in 10 minutes.

The answer is (e) 746 MJ.

5. The power used by a device can be calculated using the formula:

Power = Energy / Time

Here, the energy consumed by the hair dryer is given as 90 kJ (kilojoules) in one minute.

Power = 90 kJ / 1 minute

To perform the calculation, we need to convert the energy from kilojoules to joules and the time from minutes to seconds:

Power = 90,000 J / 60 s

Power = 1500 J/s

Power = 1500 W (since 1 watt is equal to 1 joule per second)

Therefore, the power used by this hair dryer is (c) 1500 W.

d

d
a
c
a