Work and Power Questions

This textbook makes everyone in the high school world struggle. However, I can help with the dreadful 2 star Cutnell and Johnson Questions. People think these Cutnell and Johnson 2 star questions are literally impossible to solve, but with simple critical thinking it is a peace of cake. Every single student who has ever taken physics has dreaded these questions assigned for homework, but if you try you can solve anything.

Before each question, a tutorial will be given that would help the student solve the problem. Explanations and formulas would be given prior to each example question. However for this question a tutorial should not be needed since it is a very basic topic. Once we get deeper into physics, even parts after AP Physics, we should make sure we pay attention to the tutorials, as they are essential for the completion of the question successfully.

1) For example: The motor of a ski boat generates an average power of 7.5 * 10^4 W when the boat is moving at a constant speed of 12 m/s. When the boat is pulling a skier at the same speed the engine must generate an average power of 8.30 * 10^4 W. What is the tension in the tow rope that is pulling the skier?
What my teacher always told us was to write down everything that you know and all of the stuff you want to know. Also she told us to write down what the formula needed in order to solve the question.

What we know
Power = 8.30 * 10^4 W (with the skier)
Power = 7.5 * 10^4 W (without the skier)
Velocity = 12 m/s (constant)

What we want to know
The tension of the rope pulling the skier.

What formula is needed to solve this equation

Power = Work / Time = Force * Velocity
Work = Force * Distance

Steps to Solve the 2-Star Cutnell and Johnson Question

The amount of power needed to pull the skier can be found by subtracting the powers with the skier and without the skier.

8.30 * 10^4 W (with the skier) - 7.5 * 10^4 W (without the skier) =8 * 10^3
Since the Power = Force * Velocity, the tension (force) can be found by plugging in the units and solving this equation.
Tension = (8 * 10^3 W)/(12 m/s)
Tension = 666.6 Newtons
BOOM! You solved one of the hardest physics problems that you will ever attempt in high school.

Now that I introduced the Cutnell and Johnson 2-Star question (aka the hardest questions in the book), from now on I recommend you, the students, to actually attempt to solve the question before looking at the summary. So this means you should cover up the answer and solve the question before looking onwards. This is VERY important for your success in physics. Please subscribe and you will be given tutorials and practice problems every week.

Open up this picture and study it since it gives valuable information on Work, Energy, and Power.