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

Ah, first you try and it is too late because I have to go to sailing practice. Maybe Steve will help.

abcd

1. To determine which energy transformation best describes the operation of a solar powered battery charger, we need to understand how solar powered battery chargers work. Solar chargers typically use photovoltaic cells, which convert sunlight (radiant energy) into electrical energy.

Looking at the options:
(a) electrical energy --> thermal energy --> kinetic energy: This does not apply to solar powered battery chargers, as they do not involve thermal or kinetic energy transformations.
(b) nuclear energy --> potential energy --> chemical energy: Nuclear energy is not involved in solar powered battery chargers.
(c) thermal energy --> elastic potential energy --> electrical energy: There may be a small amount of thermal energy involved, but elastic potential energy is not relevant to solar powered battery chargers.
(d) radiant energy --> electrical energy --> chemical potential energy: This option is close, but the final transformation is incorrect. Solar chargers convert radiant energy (sunlight) into electrical energy, but they do not convert it into chemical potential energy.
(e) radiant energy --> thermal energy --> electrical energy: This option accurately describes the energy transformation in a solar powered battery charger. Radiant energy (sunlight) is converted into thermal energy and then into electrical energy.

Therefore, the correct answer is (e) radiant energy --> thermal energy --> electrical energy.

2. To find the kinetic energy gained by the rocket in the first 50.0 cm of takeoff, we can use the kinetic energy formula: KE = 0.5 * mass * velocity^2.

First, we need to determine the velocity of the rocket. To do this, we can use Newton's second law, F = ma, where F is the thrust force applied by the jet engine, m is the mass of the rocket, and a is the acceleration.

Since the force of air friction is negligible, the net force acting on the rocket is equal to the thrust force. Therefore, we have:

F = ma
21.0 N = 0.500 kg * a

Solving for a, we find that the acceleration is 42 m/s^2.

Next, we can use the kinematic equation s = ut + 0.5at^2 to find the distance traveled by the rocket in the first 50.0 cm. Since the rocket starts from rest (u = 0), the equation simplifies to s = 0.5at^2.

Plugging in the values, we have:

0.5 * 42 m/s^2 * (0.50 m)^2 = 5.25 J

Therefore, the kinetic energy gained by the rocket in the first 50.0 cm of takeoff is approximately 5.25 J. The closest answer choice is (a) 4.0 J.

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

The work done on an object can be calculated using the equation W = F * d * cos(theta), where W is the work done, F is the force applied, d is the distance over which the force is applied, and theta is the angle between the force and displacement.

In this case, the force applied horizontally is 300 N for a distance of 2 m. The angle between the force and displacement is 0 degrees because the force is applied horizontally.

Therefore, the work done on the crate by the applied force is:

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

The work done against friction can be calculated using the equation W_friction = F_friction * d, where F_friction is the force of friction and d is the distance over which the crate is pushed against friction.

In this case, the force of friction is 200 N for a distance of 2 m.

Therefore, the work done against friction is:

W_friction = 200 N * 2 m = 400 J

The total work done on the crate is the sum of the work done by the applied force and the work done against friction:

Total work = W_applied + W_friction = 600 J + 400 J = 1000 J

Since work is equal to the change in kinetic energy, the final kinetic energy of the crate is equal to the total work done on it:

Final kinetic energy = 1000 J

Therefore, the correct answer is (e) 300000 J.

4. To find the energy produced by the engine in 10 minutes, we can use the formula:

Energy = Power * Time

First, we need to convert the power from horsepower (hp) to watts (W). Since 1 hp is equal to 746 W, we have:

Power = 10 hp * 746 W/hp = 7460 W

Next, we convert the time from minutes to seconds, as energy and power are typically measured in joules per second (Watt-seconds or Joules). Since there are 60 seconds in a minute, we have:

Time = 10 minutes * 60 seconds/minute = 600 seconds

Finally, we can calculate the energy produced by multiplying the power and time:

Energy = 7460 W * 600 s = 4,476,000 J or 4.476 MJ

Therefore, the correct answer is (d) 4.5 MJ.

5. Power is defined as the rate at which energy is consumed or produced. To find the power used by the hair dryer, we can divide the energy consumed by the time taken.

Power = Energy / Time

First, we need to convert the energy from kilojoules (kJ) to joules (J). Since 1 kJ is equal to 1000 J, we have:

Energy = 90 kJ * 1000 J/kJ = 90,000 J

Next, we need to convert the time from minutes to seconds. Since there are 60 seconds in a minute, we have:

Time = 1 minute * 60 seconds/minute = 60 seconds

Finally, we can calculate the power by dividing the energy by the time:

Power = 90,000 J / 60 s = 1500 W

Therefore, the correct answer is (c) 1500 W.

D

A
B
C
A