Unformatted text preview: p [O \ZSOEQTJ. was {31 Walker 01. A ball is thrown horizontally from the top of a building. What will be its vertical
displacement from the top of building 2.0 seconds after it leaves your hands? [A] 4.9 m [B] 9.8 m " [C] .6 m [D] 40.2 111 [1—3] 52.4 m
y 2 y0 + vat +%at2 y—yo =0—4.9m/szt2 =19.6m "remeiléloiqli 02. When a parachutist jumps from an airplane, he eventually reaches a constant speed, called
the terminal velocity. This means that [A] the acceleration is equal to g. [B] the force of air resistance is equal to zero.
[C] the eﬁ‘ect of gravity _ ‘ down. [D] the effect of gravity increases as he becomes
closer to the ground. ‘1 [E] e force of air resistance is equal to the weight of the parachutist. 03. In the ﬁgure, masses m1 and m; are such that in. > m; and they lay on a level, frictionless surface. We can apply a horizontal force l: either from the left or from the right. The contact
force between masses In] and m; is [A] zero newtons.
[B] larger when it is applied from the left. II e same in either case.
‘@ arger when it is applied from the right.
impossible to determine based on this data. 04. A 45kg person steps on a scale in an elevator. The scale reads 460 N. What is the elevator doing?
[A] The elevator is in free fall. [B] None of these.
/‘ is accelerating downward at 0.41 mfsz. [D] It is stationary.
/ [E] I is accelerating upward at 0.41 III/82.
A ~ W = ma “ WA —W _ 460N—441N
m 45kg a =+0.41m/s2 05. If a vector has components Ax < 0, and A, < 0, then the angle that this vector makes with
the positive xaxis must be in the range [A] 0° to 90°. [B] 90° to 180°. [C] l 0° to 270°. [D] 270° to 360°.
[E] none of these 7. 06. A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the
velocity of the rock right before it hits the ground? [A] It is equal to ' 1m '31 vertical velocity. [B] It is equal to its initial horizontal
velocity. 5 [C] [ 3 equal to the magnitude of its initial velocity. [D] 0
[E] none of these_ 07. Florida Power & Light bills customers in kilowatthours (kWh), which is a unit of energy. If
a residential customer uses 2500 kWh per month, how many kWh does this household use per
second? (Assume 1 month = 30 days) [A] 0.058 rt/ [B] 9 6x104 [C] 0.029 [D] 0.023 [E] none of these
ZSOOkWh. .lday 1hr =9_6x10_4
mo 30days 24hr 36005
08. The MKS unit of energy is the Joule [1 J = (l N)(1 m)]. If power is deﬁned as Eﬁergy ,
[me which of the following equations is dimensionally correct? /®=Fv [B}P=Fa [C]P=—Ii [D]P=E [E]noneofthese
; I m V P: :Fv S 1020W
09. The MKS unit of power is the watt (W). If the Sun provides 2 (on average) in In
Miami, what is the area of a solar panel operating at 80% efﬁciency that would be needed to provide the 2500 kWh per month used by the residential customer above? (lkWh =3.6X106 J ) [A] 2.721112 [B]3.06 m2 [C]4412m2 @2511? [E] none ofthese
1m2 ‘1W‘3.6x1061.9.6x104kWh_42m2
1020w(0.8) lJ/s kWh s ' 10. The average speed of a coconut during a 25 fall from a tree, starting at rest is [A] 19.? rm‘sv [B] 9.8 W52 [C] 39.2 mfs If [D] 9 8 mfs [E] none ofthcse liravrvr—V0 =gt—~_0=9.8m/s ""e—
All t 11. A person walks 8.0 rn in a straight line east of north and ends up 4.0 or east and a certain
distance north. HOW many degrees east of north has the person walked? / l: [A] 3(9 [B] 45° [C] 60° [D] 75° [E] 90° \ ,../ N We are looking for 0: 0=cos ‘1 [i] =cos " = 30°
r 8m 12. A bullet is ﬁred with a certain velocity at an angle 0 above the horizontal at a location where
g = 10.0 mfsz. The initial x and y components of its velocity are 86.6 m/s and 50.0 m/s
respectively. How lon does it take before the bullet hits the ground? [A] 5.0 s @l s [C] 15.0 s [D] 20.0 s [E] none ofthese. On the way up, the yvelocity loses 10 m/s per second, so it takes 5 s up to reach zero
velocity, then it takes just as much time to come down! 13. A car traveling with velocity v is decelerated by a constant acceleration of magnitude a. It
travels a distance d before coming to rest. If its initial velocity were doubled, the distance
required to stop would 11] do ble as well. [B] decrease by a factor of two. [C] stay the same.
[D] q le. [E] decrease by a factor of four.
\__
vf2 — v02 = ZaAs = 2ad
0 — v 2 v 2 2v 2
cl: 0 =i —> LetV0—>2V0:d'=( 0) =4d
2(na) 23 2a 14. From the edge of a roof top you toss a green ball upwards with initial velocity v0 and a blue
ball downwards with the same initial velocity. When they reach the ground below, [A] the green ball will be moving faster than the blue ball.
. blue ball will be moving faster than the green ball.
. [C] the balls will have the same speed. ere is not enough information to answer this. The green ball goes up to its maximum height and then falls back down again. When it
reaches the same point as that from which it was thrown, by the laws of symmetry, it will
have exactly the same magnitude of velocity, but directed downward! So both the green
and blue balls have exactly the same dawnward velocity at the edge of the roof. Naturally,
they will have exactly the same velocity just before the hit the ground. 15. Dr. Zane’s favorite romantic mavie is [/[A' I m'c [B] Sleepless in Seattle [C] The English Patient
/ [D] Ali 1: vs. Predator [E] Love Actuale had to attend class to know this answer! © 16. On a training mission, the crew of a Black Hawk helicopter are cruising east (+i)at an airspeed of 120 knots (I knot = 1 nautical mileth = 1852 mfhr = 0.5144 mfs) and an altitude of
1200 111. Up ahead (further to the east), the pilot spots their target on the ground and a crew
member prepares to release a grenade (on = 0). [A] At what horizontal distance from the target should the grenade be released?
x=v0xt —+y=y0+v0yt+%at2 0:1200m+0—5m/szt2 t= 29931321555
4.9m/s x = (61.7m/s)(15.55) =957m [B] If, instead of just releasing the grenade, the crewman throws it straight down with a velocity
of 20 mfs, at what horizontal distance from the target should this occur? ~1200m :(—20m/s)t—5m/s2 t2
59 +20t—1200=0 2
t=—20:,/(20) H4(5)(—1200) :13.“ 25
x = (61.7m)(13.6s) = 840m 17. A crate of mass 50.0 kg sits on the ramp ofa loading dock. (Use g z 10 mfsz)
a. If the ramp is inclined at an angle of 30.0°, ﬁnd the normal force acting on the crate.
b. If we assume that the surface of the ramp is smooth (no friction), ﬁnd the force that a
worker would need to apply parallel to the surface of the ramp (x’axis) in order to push the
crate up the ramp at constant velocity.
c. If the worker applies a force parallel to the xaxis, ﬁnd the magnitude of the force needed
to accelerate the crate up the ramp at 1.5 mfsz. a. 2F), = NmgcosB=0 J. N = (50.0kg)(10m/52)73 : 433N b.ZFx. = Fb —mgsin8=0
Fb = (50.0kg)(10m/52X.5) = 250N
c. 21*}: FC 0059— mgsinB = ma m(a + gsin e) _ (5t).01<g)(1.5m/s2 +10m/sz(.5)) F =
c cosB (0.866) =375N ...
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 Spring '08
 Ashkenkai
 Physics

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