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Physics 220 — Exam #2 i.
October 15 2000
This exam consiste of 12 problems on 7 pages. Please check that you have them ail.
All of the formulas that you will need are given below. You may also use a calculator.
sind = pir core = zfr tan = y fz
t
average speed = ‘lstunce srortled 9 = 9.8 m/s }
1 mik = 1.5 km Z|
average velocity = 7 = “iablecmem
instantaneous. velocity = slope of positian versus time
instantaneous sceeleration = alope of velocity versus time
For constant ecceleration:
B= To + ut + Jat?
uv = th + at
vw? = of +2ale — x5)
F = ma
FitSim = dsV (static friction) Fyrinen = tt N (sliding friction)
Ferity = 4 @ = 667 107"! Nu? /kg?
a, = wfr KE = jm
Ws Fd cose PE parity = ™mGh power = work/A?
p= mit &p = impulke = F At
1. A rollercoaster starts at the top of its track (point A} with a speed of 10 m/s. What
will its apeed be when tt reaches point BY Assume that friction is negligible and ignore
the kinetic energy of the wheels.
damyh
(a) 22 nfs Lia eK ohs > fo f bP f
tb} 6.6 mis 7?
{ck 12 m/s L ze zf a
(d} 10 m/s Ve a Va Feo
r= limes
Wp = jlo er 2CEH CRS I [oe4
2. Consider a robber ball as itis deopped so as to bounce from a horizoutal concrete floor.
If the ball has a speed of 4.0 m/s just before etriking the Aoor, and a speed of 2.5 m/s
just after bouncing, find the average force of the floor on the ball. Assume that the
ball is in contact with the floor for 0.125, and that the masa of the ball is 0.15 kg.
fa} 3.1 N 9 ve Apet 29
—» G ee PA 5S oe ga
ec] 0. TH AT
(@) 53.N 77"
(e] 0.89 fat = Ape woeo “a
ox cf
9S TE
po ae
= OF fs OZ GW
we C Gtk,
7. A rubber ball of mage 0.12 kg ta dropped from a height of 1.4m above the floor. If
the ball bounces back up to a height of 1.1 m, find the change in the total mechanical
energy of the ball.
h
ert Aewp nan
() 133 ow ak
p12) EAA
aa ~ 0, 12 (99) (oF)
= OPT
—
8. A car of mass 1200 kg ip moving along a circular arc of radiue 35 m. Lf the apaad of
the car is 12 m/e, find ita centripetal acceleration.
(a) 4900 m/s? 3
irae OL yay
—>
(d) 34 m/e P ——
9. A baseball pitcher throws a pitch to a batter, and gives the ball (of maza 0.20 kg) an
initial speed of 45 m/s. The batter makes contact, and sands the ball in the oppoaite
direction with a speed of 35 m/s. What is the magnitnde of the momentum of the ball
just after it is hit?
(a) 16.0 N-s
{b) 9.0N P = “ b
= = V0 4 uf
__pciiiee> | s p20 (>
@ 20 tem/s 0 enna
(e) zero
10. A rock of mass 3.3 ke is tied to a string of length 1.2m. The rock is held at rest as
shown 60 that the string is initially tight, amd then released. Find the speed of the
rock when it reaches the lowest point of ite trajectory.
LE ®@ we £242
A
poo eet
F zu h
= bey tee
fa) 34 L ha Fa Ke ;
Buse Lyfe 1 1
(ch 23 m/s 0 v
td) 7.7 m/s
(e} O73 m/s 2 h
w= 24 A
f “Fen
=), (arte?) 54
“Up x tgha
1i, A satellite is put into orbit around the earth. If the period of the orbit iz 90 minutes,
and the radius of the arbit is 6.8 x 10° m, find the speed of the satellite.
(a) 450 m/s ¢
(b} 2.9.x 10° m/s ar (bb kts 5
fe) 1.8% 10? m/e awk a
—b Wiaxtee> Y= To * 90. bo
(e} 4.7 x 10¢ m/s
= 7700 "4%
12, A baseball pitcher throws a pitch at a speed of 45 m/s. if the ball has a masa of 0.2 ke,
find the work done by the pitcher on the bell.
(a) 2000 J oka %
(b) 18] hi = AKE > Lite 3 we
P< ar t
(a) 2.0N 2 °
fe) 45] ch fOI) 4S = 20T
2h —————_———
The End
