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Unformatted text preview: Physics 1A —SQring 2009
lst MIDTERM TEST  Wed, April 22, 2009 This exam is closed book. One 3 inches X 5 inches card with formulas (two sides) is allowed. Write all units for all numerical results. For full credit on a calculation, always show your work to
get your answer. Please make a box around your ﬁnal question to each answer. The exam consists of a set of 4 short questions and 2 problems.
Please do not open the exam until we do it all at the same time. You will have 50 minutes.
Good luck! NAME: — — — — — — — _ — — _ — _ — — — — — — _ _ a — a ~ _ _ — — _ _ a _ _ _ — STUDENTLD; — — — — — — — — — — i — — — h ﬂ _ _ _ — _ _ _ _ _ _ u * __ SIGNATURE:~ “— — — — — — _ _ _ _ _ _ _.__.
Max I
Po i'r'd's J P0 {n+5 . . .I..._..___..._‘ First: a set of 4 short questions (20 points in total)
(1.) (6 points) l—e Lb 1—0 The following is the plot of the onedimensional displacement of a body as function of time,
durng 40 seconds (give both magnitude and Sign in your answers). 36 (In) Straight
line Parabola 10 15 20 25 30 35 40 MS) what is the average velocity of the body during the first 30 s time interval?
what is the average speed of the body during the 40 s time interval? 13 the body accelerated during the ﬁrst 5 seconds? If it is, which is the sign of the acceleration? 71):: 0'5 ﬂ : /7 wife a 5 .5
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5‘06 5 (2) (4 points) A man of mass M and his parachute of mass II] are falling with terminal velocity, due to the
resistance force of the air of magnitude clvg.
2—3, ‘vVhat is the net force acting on the man?
2—b What is his terminal speedCin terms of M, m, c; and g)? —a "jg—Om Pump" 2 0 (3) (6 points]I A 100 kg man is riding on a Ferris Wheel of radius of 10111 at a constant speed of 10 m/s. For this question, take the acceleration of gravity to be 9 = 10 m/sg. When he is at the top of the
ride,
321 is he accelerating? If so, which is his acceleration?
313 What is the “apparent weight” of the man at that moment? _ _ = E 111 = WE _—_
“Ema £0, E " 5y 52' a 3 ’10 '11 affﬂjmad‘ a: (4) (4 points) An airplane is ﬂying at 100 km/h in directiou North East (at 45 degrees from the
North direction) with respect to the air. There is a strong wind of 70 km/h towards the West. In which direction is the plane traveling with respect to land? (give the angle with respect to the
North direction) (5) A problem (30 points total—10 each question)
A cannon is been ﬁred from the top of a castle well. One cannonball
30" with re3pect to the horizontal with a. speed of 50 m/s. A secon accidentally dropped hits the grounds below in 1.5 s. The” ground ere
5a is ﬁred at an angle of
d cannonball that was
und the castle is level. How high is the top of the castle wall with respect to the ground?
5~b How far from the castle well does the ﬁrst cannonball hit the ground?
5—C With what speed does the first cannonball hit the ground?
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in] 2 La“ h:.g_t=_a_§'(r.5)5£1=llm
9:50“ 2 2 5 2 ...__ _ l
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.5 (B) A problem (30 points— 10 each question) A plank inclined at an angle 6 with respect to the horizontal is being lifted vertically up with an
acceleration a, : 2111/52. The plank has a 1 kg box on top oi’it. The coefﬁcients of static
friction between the surfaces of the plank and the box are n, =
6—3. and kinetic
0.5277 and in, = 0.300 respectively. The box is not sliding. What is the friction force
the force diagram) acting on the box if 6' = 20 degrees? {Show
Gal) If the angle 6? is now increased, which is the l
slide? (show the derivation starting from Ne B—c
Assume that increasing just a bit the
box starts sliding, wl
_ down the inclined pl argest angle (9mm for which the box will still not
wton's second law) angle, so that we can still say that the angle is ﬁlm“, the 1ich is now its total acceleration (notice that now the box is accelerated
ane and also upwards with a = 2111/52) a2 1"
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 Spring '10
 peroomian
 Physics

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