PHYS 2101 Midterm: PHYS 2101 LSU 2007s f
Physics 2101, Final Exam, Spring 2007
May 10, 2007
Name :
Section: (Circle one)
1 (Rupnik, MWF 7:40am) 2 (Giammanco, MWF 9:40am)
3 (Rupnik, MWF 11:40am) 4 (Rupnik, MWF 2:40pm)
5 (Giammanco, TTh 10:40am) 6 (Gonz´alez, TTh 1:40pm)
•Please be sure to write your name and circle your section above.
•For the problems, you must show all your work. Let us know what you were thinking when
you solved the problem! Lonely right answers will not receive full credit, lonely wrong answers
will receive no credit.
•For the questions, no work needs to be shown (there is no partial credit).
•Please carry units through your calculations when needed, lack of units will result in a loss
of points.
•You may use scientific or graphing calculators, but you must derive your answer and explain
your work.
•Feel free to detach, use and keep the formula sheet. No other reference material is allowed
during the exam.
•GOOD LUCK!
1
Problem 1 - 13 points
Two blocks of masses M and 2M are connected to a spring of constant kthat has one end fixed,
as shown in the figure. The horizontal surface and the pulley are frictionless, and the pulley has
negligible mass. The blocks are released with the spring relaxed.
(a) (3 pts) Write an expression for the work done by gravity on the M hanging block when it
reaches the lowest position, a distance Hbelow its initial position, where it momentarily
stops. Your expression should be in terms of M, g, H and numerical constants.
(b) (4 pts) Write an expression for the work done by the spring when the M block reaches the
lowest position, using k, H and numerical constants.
(c) (6 pts) Derive an expression for the maximum distance Hthe spring stretches after the blocks
are released, in terms of M, g and k.
2
Question 1 - 6 Points
In the figure below, block 1 slides from rest along a frictionless ramp from height hand then collides
with stationary block 2, sticking to it. After the collision, the blocks now stuck together, slide into
a region with a coefficient of kinetic friction µk, and come to a stop in distance dwithin that region.
(a) (2 pts) Circle the quantity (or quantities) that are conserved in the fall of block 1 before the
collision:
Mechanical energy Linear momentum Neither
(b) (2 pts) Circle the quantity (or quantities) that are conserved for the system of blocks 1 and
2during the collision:
Mechanical energy Linear momentum Neither
(c) (2 pts) Circle the quantity (or quantities) that are conserved in the motion of the blocks after
the collision, until the blocks stop:
Mechanical energy Linear momentum Neither
3
Document Summary
6 (gonz alez, tth 1:40pm: please be sure to write your name and circle your section above, for the problems, you must show all your work. Let us know what you were thinking when you solved the problem! No other reference material is allowed during the exam: good luck! Two blocks of masses m and 2m are connected to a spring of constant k that has one end xed, as shown in the gure. The horizontal surface and the pulley are frictionless, and the pulley has negligible mass. In the gure below, block 1 slides from rest along a frictionless ramp from height h and then collides with stationary block 2, sticking to it. Neither (b) (2 pts) circle the quantity (or quantities) that are conserved for the system of blocks 1 and. Neither (c) (2 pts) circle the quantity (or quantities) that are conserved in the motion of the blocks after the collision, until the blocks stop:
