Finding power without given speed or time

In summary, the lawn tractor in figure 18 is traveling up a hill at a constant velocity and the task is to calculate the power developed by the tractor. With a mass of 120.0 kg, an angle of incline of 21 degrees, and a distance of 12.0 m, the only given value is the constant velocity. Using the equation mgsinθ to calculate the force in the direction of down the slope, which is 421.4N, we can determine that the net force is zero since the acceleration in the direction of the slope is 0 m/s^2. This means that the motor must produce 421.4N of force. However, since no value for velocity or time is
  • #1
J51mustang
1
0

Homework Statement


The lawn tractor in figure 18 goes up a hill at a constant velocity. Calculate the power that is developed by the tractor.
Mass: 120.0 kg
Angle of incline: 21 degrees
Distance: 12.0 m
Velocity: no velocity given other than it is constant
Time: idk

Homework Equations


None really

Just note that I used 9.8ms^-2 for acceleration due to gravity, NO value for velocity was given, and no time value was given.

The Attempt at a Solution


So I calculated the force in the direction of down the slop (by using mgsin21) and got a force of 421.4N, which means, since the acceleration in the dimension of the slope is 0ms^-2, that the net force is zero, meaning that the motor produces 421.4N of force. Now from here I’m stuck, as no value for velocity is given other than that it’s constant, and idk how to calculate time without velocity so that I could calculate power. Pls help.
 
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  • #2
J51mustang said:
Mass: 120.0 kg
Angle of incline: 21 degrees
Distance: 12.0 m
Constant velocity
If that is all you are given then there is clearly not enough information. Make very sure there is no information you have overlooked. Some detail in the figure, perhaps?
 
  • #3
Hi J51mustang,

Welcome to Physics Forums!

Since no velocity is given it looks like you'll have to provide a symbolic answer rather than a particular numerical result...
 

FAQ: Finding power without given speed or time

1. How do you find power without given speed or time?

The formula for power is P = W/t, where P is power, W is work, and t is time. So, if you have the work done by a force and the amount of time it took to do that work, you can calculate the power. However, if you do not have either the speed or time, you cannot calculate power.

2. What is the relationship between power, speed, and time?

Power is directly proportional to both speed and time. This means that as speed or time increases, power also increases. This relationship can be represented by the equation P = W/t, where power is equal to work divided by time.

3. Can you give an example of finding power without given speed or time?

Yes, for example, if you know that a car has an engine that produces 300 horsepower and it can travel 400 miles on a tank of gas, you can calculate the power of the engine. Since power is equal to work divided by time, we can rearrange the equation to solve for time. So, time (t) = work (W) divided by power (P). In this case, the work is the distance traveled, which is 400 miles. Therefore, the power of the car's engine is 400 miles divided by 300 horsepower, which equals 1.33 hours.

4. Is it possible to find power without given speed or time in all situations?

No, it is not possible to find power without given speed or time in all situations. As mentioned earlier, the formula for power requires either speed or time to be known. Without either of those values, power cannot be calculated. However, in some cases, it may be possible to estimate power based on other factors, such as the type of machine or equipment being used.

5. How is power measured without given speed or time?

Power can be measured using a device called a dynamometer, which measures the torque and rotational speed of an engine or motor. By measuring these values, power can be calculated using the formula P = T x ω, where P is power, T is torque, and ω is angular velocity. However, this method still requires at least one of the values (torque or angular velocity) to be known, so it may not be possible to measure power without given speed or time.

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