Work, Energy, and Power unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Conservative forces and path independence
Gravitational potential energy in general
Net work and the work–energy theorem
Kinetic energy in terms of momentum
Deriving force from U(x)
Elastic potential energy
Where the factor of one half comes from
Kinetic energy is a scalar
Work done by a variable force from a graph
Units of energy and power
Circular orbit energy relations
Energy in a spring-mass system
Short answer 1. Define or explain: Turning points from a U diagram
3 ptsShort answer 2. Define or explain: Instantaneous power
3 ptsShort answer 3. Define or explain: Work as a dot product
3 ptsShort answer 4. Define or explain: Work as an integral
3 ptsFree response
10 ptsStudents investigate the coefficient of kinetic friction between a block and a horizontal surface. They give the block an initial speed v₀ and measure the distance d it slides before coming to rest. They repeat the experiment for several initial speeds. v₀ (m/s) 1.0 1.5 2.0 2.5 3.0 d (m) 0.15 0.33 0.60 0.92 1.32
A(i). Describe a procedure the students could use to give the block a measurable, repeatable initial speed. A(ii). Describe one step that would reduce experimental uncertainty.
B(i). Derive an expression relating the sliding distance d to the initial speed v₀ and the coefficient of kinetic friction μ_k. B(ii). Indicate what quantities the students should graph to obtain a straight line usable to determine μ_k.
C(i). Calculate the values to be plotted on the horizontal axis. C(ii). Describe the axis labels, with units, the positions of the plotted points, and the best-fit line.
D. Using the best-fit line described in part C, calculate an experimental value for the coefficient of kinetic friction.