Question
8) A load generates a force of 300 Newton's. Calculate the mass of the load. a) 3.6 kg b) 3060 kg 306 kg 30.6 kg 9) Lifting a load an electric motor uses 180 ,000 Joules of energy in 11/2 minutes. (L3.4) is the power rating of the motor? 500 W b) 1 kW c) 1.5 kW d) 2 kW (L3.4)
Answer
4.7
(264 Votes)
Yale
Elite · Tutor for 8 years
Answer
*Question 8*In first question, substitute the given values in to the
which is
Copmpute it and round to nearest tenth, which gives: (क) ≈ 30.6kg*Question 9*Next, substitute the values into the power equation:\( P (in Watts) = \frac{180,000 J}{90s} \)Conversion from Watts to kilowatts results 2,(1 W=0.001kW).Which gives the final rating of our motor power output:d) 2 kW
Explanation
## Step1:First, we will solve the question number 8. The concept applied here is Newton's second law, which states that force (F) equals mass (m) times acceleration (a). Acceleration due to gravity is approximately 9.8 m/s squared on Earth. Given force, we can rearrange the equation to solve for mass. The formula used here is:###
where:m = mass in kgF = force in Newtonsg = acceleration due to gravity (~9.81 m/s squared on Earth)## Step2:Substitute the given values into the equation.## Step3:Now onto the second question. It is asking for the power rating of a motor given it use a certain amount of energy in a certain amount of time. The formula we use here is the one for power, which is given by: ###
where:P = Power in watts, W = work in Joules,t = time in seconds.First, we convert the time from minutes to seconds, which gives 90 seconds, so now time t = 90s. Now that we have all the necessary units in their proper dimensional forms, they may be substituted into our power formula. ## Step4:Substitute in the power formula the given values and simplify the equation to find the power in Watts. Then, convert it to kilowatts for the answer.