What is the rate of energy transfer to the lift?

Question image

Understand the Problem

The question is asking for the calculation of the rate of energy transfer (power) to a lift with a specified mass going up at a constant velocity. Given the mass of the lift and the acceleration due to gravity, we will use the formula for power, which is the product of force and velocity.

Answer

The rate of energy transfer to the lift is $18.1 \, \text{kW}$.
Answer for screen readers

The rate of energy transfer to the lift is $18.1 , \text{kW}$.

Steps to Solve

  1. Identify the formula for power We will use the formula for power, which is given by:

$$ P = F \times v $$

where ( P ) is power, ( F ) is force, and ( v ) is velocity.

  1. Calculate the force The force acting on the lift due to gravity can be calculated using:

$$ F = m \times g $$

Where:

  • ( m = 540 , \text{kg} ) (mass of the lift)
  • ( g = 9.80 , \text{m/s}^2 ) (acceleration due to gravity)

Now, substituting values:

$$ F = 540 \times 9.80 $$

  1. Substitute the values to find the force Let's calculate the force:

$$ F = 540 \times 9.80 = 5292 , \text{N} $$

  1. Calculate the power Now that we have the force, we can substitute it back into the power equation:

$$ P = F \times v $$

This means substituting ( F = 5292 , \text{N} ) and ( v = 3.4 , \text{m/s} ):

$$ P = 5292 \times 3.4 $$

  1. Calculate the power Now, performing the multiplication:

$$ P = 5292 \times 3.4 = 18096.8 , \text{W} $$

  1. Convert power to kilowatts Since power is required in kilowatts (kW), we convert watts to kilowatts by dividing by 1000:

$$ P = \frac{18096.8}{1000} = 18.1 , \text{kW} $$

The rate of energy transfer to the lift is $18.1 , \text{kW}$.

More Information

The calculated power indicates how much energy is needed to lift the mass at a constant velocity. Power is a measure of energy transfer over time, and here it reflects the efficiency in moving the lift against the force of gravity.

Tips

  • Forgetting to convert from watts to kilowatts is a common mistake; always remember to divide by 1000.
  • Confusing the units of force (newtons) and power (watts), which can lead to incorrect calculations.

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