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Unformatted text preview: Physics 7A Midterm #1, Lecture Section 2, Fall 2006. ©A. Zettl
All Problems Worth 20 points. One side of one sheet notes (81/2" x 11") allowed. Good luck. 1. A small crazy squirrel runs along the nearly ﬂat ground at speed 2.0m/s onto a large, ﬂat, frozen mud
puddle whose surface is absolutely frictionless. Somewhere near the middle of the puddle the squirrel jumps up
and reaches a maximum height 1.23m above the ice surface. a) Determine the total time the squirrel is in the air (i.e. time between jumping and landing). b) Determine the horizontal distance between the jumping and landing spots on the ice. c) Determine the speed of the squirrel just before it lands. 2. A car of mass M will be towed along a roadway uniformly inclined at angle (F)1 by means of a (massless)
cable attached to a powerful tow truck. The cable makes an angle 92 with respect to the roadway. The tow truck
starts from rest. What is the greatest distance Lmax along the roadway that the car can be towed in the ﬁrstbt
seconds if the cable has a breaking strength Tm? Remember, M, 91, 62,me, and 5t are all known quantities.
Also, neglect frictional forces on the car (you may treat the car as if it slides without friction). 3. A crate slides down a rightangled trough inclined at angle 9 as shown in the ﬁgure. The coefﬁcient of kinetic friction between the crate and the material composing the trough is yk. Find the magnitude of the
acceleration of the crate down the trough. /.90°\ 4. Five blocks all of different mass are connected by massless (nonstretching) string segments as shown: The
pulley is massless and frictionless, and the horizontal table on which M1 and M2 slide is frictionless. Grav1ty g, vertically directed, acts on the blocks. A
8) Detcrfnine the horizontal acceleration vector of M1. W M 1 AN
b) Find the tension T in the string segment connecting M3 and M4. 1 /\
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1 Mb“ 5. The plot below ShOWS the velocity versus time of a point particle moving in one dimension. Since v is always positive, you may assume the particle always moves in the +x direction. Assume that at t=0 the particle is
at x=0. Make corresponding plots of a) position x (in meters) and b) acceleration a (in m/secz) versus time for the partide, for the same time range (0 to 10 seconds). In both cases you should mark the axes explicitly with
numerical values. Y0ur plots must also clearly show what happens at t = 2, 4, and 6 seconds. 60 A £40
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M5 3" "‘" Adel up all, Hue ec‘uOd't'ons G +@+@+@+@ awoL cancel. 6L(L +ke Tensn’ons , we. 39,1;
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Ml+ML1Msfln¢Mk T3 Zeltl.nb Fa 5 400 100 ~ 10 ﬁ ...
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