High School Physics : Understand Power
年代tudy concepts, example questions & explanations for High School Physics
Example Questions
Example Question #1 :Power
A
Power is equal to the work done divided by how much time to complete that work.
工作= the change in kinetic energy of an object.
We can solve for the work by solving for the change in kinetic energy.
年代ince the initial velocity is
We can now plug this into the power equation.
The average power is
Example Question #1 :Power
Of the following, which is not a unit of power?
Watt
newton meter /second
watt/second
joule/second
watt/second
The unit for power is the Watt. A watt is a measure of the Joules per second that an object uses. Joules can also be written as Newton Meters. Therefore a watt could also be considered a Newton Meter/Second. The incorrect answer is the watt/second since watt is the base unit of power on its own.
Example Question #1 :Power
To accelerate your car at a constant acceleration, the car’s engine must
Maintain a constant turning speed
Develop ever decreasing power
Maintain a constant power output
Develop ever increasing power
Maintain a constant power output
Power is equal to the Work put into the system per unit time.
工作= the force acting on the object multiplied by the displacement through which it acts.
Therefore power is directly related to the force applied.
Force is also directly related to the acceleration of an object. A constant force will create a constant acceleration.
年代ince power is directly related to the force applied, and the force must be constant to maintain a constant acceleration, the power must also therefore be constant.
Example Question #861 :High School Physics
A bicyclist coasts down a
First we need to analyze the motion of the rider on the way down the incline. During this time, the bicyclist has a constant velocity, which means that all forces acting on him must be balanced. He has a portion of the force of gravity pulling him down the hill and the force of friction opposing his motion.
We can use components to find the force of gravity in the x direction.
年代ince the net force is equal to
Now let us consider how the bicyclist will travel when he goes up the hill. This time, the forces acting on the bicyclist are the force of gravity and friction resisting his motion and his applied force going up the hill.
The force of friction and the force of gravity are the same as when the cyclist was coasting down the hill.
The bicyclist doesn
Power is equal to the work divided by the time to complete the work.
工作= the force times the displacement through which the object moved.
We can substitute this into our power equation to get
Velocity is equal to the distance over the time.
Therefore power could be written as
Example Question #5 :Power
How long will it take an
Power is equal to the work divided by the time it takes to complete the work.
工作= the force times the displacement.
In this case the motor is lifting the piano. Therefore the force that it is exerting is equal to the force of gravity pulling the piano down.
We can now calculate the work done on the piano.
We can now plug this value into the power equation and solve for the time.
It will take
Example Question #861 :High School Physics
The quantity
The work done on the object by the force
The kinetic energy of the object
The power supplied to object by the force
The potential energy of the object
The power supplied to object by the force
Power is equal to the work divided by the time to complete the work.
工作= the force times the displacement through which the object moved.
We can substitute this into our power equation to get
Velocity is equal to the distance over the time.
Therefore power could be written as
Example Question #7 :Power
年代ome electric power companies use water to store energy. Water is pumped from a low reservoir to a high reservoir. To store the energy produced in
Assume the upper reservoir is an average of
First, we need to calculate the amount of energy produced by the power plant.
We know that this energy is stored in the form of gravitational potential energy.
If there is
Example Question #1 :Power
How many 75 W light bulbs connected to 120V can be used without blowing a 15A fuse?
18
24
12
20
32
24
Known
Power = Current x Voltage
There are
Example Question #2 :Power
A person accidentally leaves a car with the lights on. If each of the two headlights uses 40 W and each of the two tail lights 6 W, for a total of 92 W, how long will a fresh 12V battery last if it is rated at 75Ah? Assume the full 12V appears across each bulb.
7.6hr
14.7 hr
9.7hr
6.3hr
9.7hr
First, we need to determine how much current is used by the system.
If the battery is rated at 75Ah we can divide this number by the current needed by these devices to determine how long the battery would run.
Example Question #10 :Power
The bulb is brightest in the United States
The bulb has the same brightness in both locations
The bulb is brightest in Europe
The bulb is brightest in Europe
首先,让我们确定当前的数量in the bulb while it is in Europe.
We can use this information to determine the resistance of the bulb.
Now let us determine the current going through the bulb when it is in the United States assuming that the resistance is constant.
When we compare these two current values we can see that the bulb has a higher current in Europe and a lower current in the United States. This means that the bulb will be dimmer.
