Unit 6 Exam FRQ 2020 (Harper) PDF

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Unit 6 Exam: Energy, Work & Power (FRQ) DIRECTIONS: For the following free response questions, please follow all established procedures during the course of the unit in solving each problem. This includes clearly defining your system, establishing where your E  g = 0 horizontal line is, and clearly filling out any energy conservation flow diagram and using appropriate symbols for your energy equations that result. Finally, as with all take home assessments, this is to be your own work. Please refer to the Statement of Integrity for expectations regarding honesty and expectations for completing this assessment.

FRQ 1 Two empty sleds start from the same height on opposite sides of a hill. Sled A has a mass of 40 kg while Sled B has a mass of 25 kg. Assume that friction and air resistance are negligible. A diagram illustrating the situation is shown below:

a.) Using energy equations, compare the speed of the sleds at the bottom of the hill: _____ Greater for Sled A ______ Greater for Sled B Explain your reasoning (math/formula  &1  sentence)

______ Same speed for both

B. Compare the kinetic energy of the sleds at the bottom of the hill: _____ Greater for Sled A ______ Greater for Sled B Explain your reasoning (math/formula  &1  sentence)

______ Same kinetic energy for both

C. Compare the work done by the gravitational force on the sleds as they move down the hill: _____ Greater for Sled A ______ Greater for Sled B ______ Same work for both Explain your reasoning (using a Force Diagram, math/formula & 1  sentence)

D. Compare the work done by the normal force on the sleds as they move down the hill: _____ Greater for Sled A

______ Greater for Sled B

Explain your reasoning (using a Force Diagram, math/formula & 1  sentence)

______ Same work for both

FRQ 2

A roller coaster ride at an amusement park lifts a cart to point A at a height of 120 m above the lowest point on the track, as shown below. The cart starts from rest at point A, and moves with negligible friction down the incline and follows the track around the loop of radius 40.0 m. Point D is the highest point on the circular loop.

a.) Assuming that the system consists of the cart, the track and the Earth, c onstruct a qualitative energy flow diagram for the cart at positions A and D.

b.) Citing the bar chart above, explain why the release height must be greater than the diameter of the loop.

c.) Determine the speed of the cart at position D in meters/second. Consider friction on the track to be negligible . Conservation Equation:

For parts d and e, suppose that friction is not negligible. d.) How could the loop be modified to maintain the same speed at the top of the loop as found in part c? Justify your answer in a few sentences.

e.) If 25% of the initial energy at position A has been dissipated due to friction at position E, how fast is the coaster traveling at position E if the height at that location is 40 m? Conservation Equation:

FRQ 3: A hollow sphere (I = ⅔ MR2 ), mass of M and radius of R, rolls smoothly from rest down a ramp of length L at an angle of 30° with respect to the horizontal tabletop to which the ramp is fixed. (Ignore dissipated energy from sliding friction.)

a.) On the diagram below , draw and label the forces (not components) that act on the sphere as it rolls down the ramp, which is indicated by the dashed line. Clearly identify arrows that point away from the exact point at which each force is exerted (point of contact).

b.) Complete the energy flow diagram below for the Hollow Sphere-Earth system from the time when it is at the top of the ramp to the time when it reaches the bottom of the ramp.  Also, please write the conservation equation.

Conservation Equation:

c.) The hollow sphere descends down the ramp with L = 2.4 m to reach the bottom of the ramp. Using the conservation equation above, derive an equation for its linear speed at the bottom of the ramp and then calculate this value.

d.) If the hollow sphere was twice the original mass, how would its speed at the bottom compare to your answer for part c? Justify your answer in a few sentences.

e.) After the hollow sphere leaves the table, but before it lands on the ground, how do the rotational kinetic energy and translational kinetic energy of the hollow sphere change ( increase, decrease, or stays the same) ?  Explain your answer for each form of kinetic energy.

FRQ 4 A crate of mass m, initially at rest, slides down a rough ramp of length Δx and angle of inclination 𝝷. The coefficient of friction between the crate and the ramp is  k.

a.) Construct an Energy Flow diagram for the Crate-Ramp-Earth system . Also, please write the conservation equation.

Conservation Equation:

b.) Determine the velocity of the crate at the bottom of the ramp. Express your answer only in terms of the given variables Δx, 𝝷 , and  k and fundamental constants (g ). PLACE A BOX AROUND YOUR FINAL ANSWER....