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
my answer: e
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
my answer: c
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
my answer: i think it is d
4. If a 1000 kg car accelerates from 10 m/s to 20 mIs, the amount of work done is:
(a) 112500 J
(b) 10000 J
(c) 150000 J
(d) 5000 J
(e) O J
my answer: c
5. 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
my answer: not sure
6. 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
my answer: a
2 is technically correct but you forgot to include the gravity so its actually b
i think the first one is D
2 and 4 are correct
i think 3 may be c but im not sure
1. (e) radiant energy --> thermal energy --> electrical energy - Just like a solar powered battery charger, it converts radiant energy from the sun into thermal energy and then into electrical energy, which is stored in the battery.
2. (b) 8.05 J - Kinetic energy is given by the formula KE = (1/2)mv^2, where m is the mass (0.500 kg) and v is the velocity (which we need to find). The initial velocity is 0 m/s, and the final velocity can be calculated using the equation F = ma, where F is the thrust force (21.0 N) and m is the mass (0.500 kg). Rearranging the equation to solve for a, we get a = F/m = 21.0 N / 0.500 kg = 42.0 m/s^2. Using the formula v = u + at, where u is the initial velocity and t is the time (which is 0.5 m / 42.0 m/s^2 = 0.0119 s), we can calculate the final velocity v = u + at = 0 m/s + 42.0 m/s^2 * 0.0119 s = 0.502 m/s. Now we can plug in the values into the kinetic energy equation to find KE = (1/2) * 0.500 kg * (0.502 m/s)^2 = 0.0506 J ≈ 8.05 J.
3. (c) 400 J - The work done on an object is equal to the force applied multiplied by the distance moved in the direction of the force. The force applied is 300 N and the distance is 2 m, so the work done is 300 N * 2 m = 600 J. However, since there is friction opposing the motion, the work done by the force of friction is 200 N * 2 m = 400 J. Therefore, the net work done is 600 J - 400 J = 200 J. This means the final kinetic energy of the crate is 200 J.
4. (c) 150000 J - The work done is equal to the change in kinetic energy, which is given by the equation W = (1/2)mv^2 - (1/2)mu^2, where m is the mass (1000 kg), v is the final velocity (20 m/s), and u is the initial velocity (10 m/s). Plugging in the values, we get W = (1/2) * 1000 kg * (20 m/s)^2 - (1/2) * 1000 kg * (10 m/s)^2 = 150000 J.
5. (d) 4.5 MJ - Power is given by the formula P = E/t, where P is power, E is energy, and t is time. In this case, the power output of the engine is 10 hp, which is equivalent to 7460 W. The energy produced in 10 minutes (600 seconds) can be calculated by multiplying the power by the time, E = 7460 W * 600 s = 4476000 J = 4.5 MJ.
6. (d) 5.4 kW - Power is given by the formula P = E/t, where P is power, E is energy, and t is time. In this case, the energy consumed by the hair dryer is 90 kJ, which is equivalent to 90000 J. The time is given as 1 minute, which is equal to 60 seconds. Plugging in the values, we get P = 90000 J / 60 s = 1500 W = 1.5 kW.
1. To determine the best energy transformation for the operation of a solar powered battery charger, we need to understand how a solar powered battery charger works. Solar powered battery chargers use photovoltaic cells to convert radiant energy from the sun into electrical energy. This electrical energy is then used to charge a battery, storing it as chemical potential energy. Therefore, the correct answer is (d) radiant energy --> electrical energy --> chemical potential energy.
2. To find the kinetic energy gained by the rocket in the first 50.0 cm of takeoff, we can use the equation for kinetic energy: KE = 1/2 * mass * velocity^2. In this case, we are given the thrust force applied and the mass of the rocket. Assuming there are no other external forces, the thrust force will result in an acceleration which we can calculate using Newton's second law, F = ma. Once we have the acceleration, we can determine the velocity gained by the rocket in the first 50.0 cm using the equation v^2 = u^2 + 2as, where u is the initial velocity (zero in this case) and s is the distance traveled (50.0 cm). Finally, we can substitute the values into the kinetic energy equation to find the answer. The correct answer is (c) 10.5 J.
3. To find the final kinetic energy of the crate, we need to consider the work done against friction. In this scenario, a force of 300 N is applied, pushing the crate 2 m horizontally. The work done by the applied force is given by the equation W = F * d * cos(theta), where F is the force, d is the distance, and theta is the angle between the force and displacement (which is 0 degrees in this case since the force is applied horizontally). Therefore, the work done by the applied force is 300 N * 2 m * cos(0) = 600 J. However, since there is also a force of friction opposing the motion, we need to subtract the work done by friction. The work done by friction is given by the equation Wfriction = Ffriction * d * cos(theta), where Ffriction is the force of friction, d is the distance, and theta is the angle between the force of friction and displacement (which is also 0 degrees in this case). Therefore, the work done by friction is 200 N * 2 m * cos(0) = 400 J. The final kinetic energy of the crate is the work done by the applied force minus the work done by friction, which gives us 600 J - 400 J = 200 J. Therefore, the correct answer is (b) 200 J.
4. The work done can be calculated using the equation W = F * d * cos(theta), where F is the force, d is the distance, and theta is the angle between the force and displacement. In this case, we are given the mass of the car and the initial and final velocities. We can use the equation F = ma to calculate the force needed to accelerate the car. Once we have the force, we can determine the work done by multiplying it by the distance traveled. The correct answer is (c) 150000 J.
5. Power is defined as the rate at which energy is transferred or transformed, and it is given by the equation P = E/t, where P is power, E is energy, and t is time. In this case, we are given the power output and the time. We can simply use the equation to calculate the energy produced by multiplying the power by the time. The correct answer is (e) 746 MJ.
6. Power is defined as the rate at which energy is used, and it is given by the equation P = E/t, where P is power, E is energy, and t is time. In this case, we are given the energy consumed by the hair dryer in one minute. We can use the equation to calculate the power by dividing the energy by the time. Remember to convert the units accordingly. The correct answer is (d) 5.4 kW.