PHY 1001
Unit Four – Energy
Mathematical Assignment
1. A force of 100 N pushing a 10 kg box over level ground does 300 J of work on the box. Through what distance was the force applied?
Key Idea Stock of Data and
Solution
Sanity Check
2. A force of 100 N is used to raise a 10.0kg box from rest on the ground to rest on a nearby shelf 2.00 m above the ground. How much work was done in raising the box?
Key Idea Stock of Data and
Solution
Sanity Check
3. A force of 100 N is applied in pushing a stalled automobile at constant speed for a distance of 150 m. How much work (in J) was done on the car by the force?
Key Idea Stock of Data and
Solution
Sanity Check
4. A 100 kg mass is lifted 1.8 m. What is the potential energy of the mass (in J)?
Key Idea Stock of Data and
Solution
Sanity Check
5. The kinetic energy of a motorcycle and driver is 50,000 J. If their total mass is 500 kg, what is their velocity (in m/s)?
Key Idea Stock of Data and
Solution
Sanity Check
6. A 100 watt lightbulb consumes how many joules of energy in 1 second?
Key Idea Stock of Data and
Solution
Sanity Check
7. If 200 joules of energy were used in 0.1 second, how many kilowatts of power were used?
Key Idea Stock of Data and
Solution
Sanity Check
8. A spring with a spring constant of 2.0 N/m is compressed by 50 cm. How much work was done on the spring?
Key Idea Stock of Data and
Solution
Sanity Check
9. Calculate the work (in joules) done if 200 watts are used for 5 seconds.
Key Idea Stock of Data and
Solution
Sanity Check
10. Calculate the gravitational potential energy of a 10 kg mass located 5 meters above the surface of the earth?
Key Idea Stock of Data and
Solution
Sanity Check
Key Idea: Write down a one or two word statement of the physical principle which you think is the most relevant to solving the problem. Describe the elements of the problem which indicate that this physical principle might be applicable.
Stock of Data: Make a list of the numerical data you are given in the problem description. Be sure to include units. List quantities you are asked to calculate with a trailing question mark. This step may include a diagram to help organize your understanding of the problem.
I.D. Equation: Choose an equation which reflects both the key idea of your problem and information from your stock of data. You may need more than one equation.
Solve: If the equation or equations you have chosen are not already solved for you unknown, then do the algebra to accomplish this now. Be sure to show enough detail in each step so that a reader can follow your work.
Substitute in Numerical Data: Once you have an analytic solution, substitute numerical values into the analytic solution to obtain the final answer.
Sanity Check: Answer the question. “Does this answer make sense in light of the rest of the knowledge I possess?” The sanity check could include a back of the envelope calculation done with a single significant digit or a unit analysis of the final answer. How you accomplish this step will vary based on the background knowledge you already possess, but is important none the less in connecting new concepts to the knowledge you already possess.
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