Announcements I
Announcements II
1. Exam #1
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2. Special office hour tomorrow: Chan: 11am to noon
and 3 – 4 pm
Feb 18, Wednesday 8:20 pm – 10:10 pm. Please
be there at least 10 minutes early.
Material from sections 1.1 – 5.3 of Serway/Vuille,
20 questions, multiple choice
Up to gravitational potential energy – no springs
If your last name begins with A through P, you
should go to Carleton 100
If your last name begins with R through Z, you
should go to Pugh 170
You are allowed one handwritten formula sheet
(both sides), 8 ½”x 11”paper
Bring #2 pencil, eraser, a calculator and ID.
Sample exam from last semester posted on
website
3. HW set #5 is not due until Feb 25
Note: Exam 1 may include material that is covered
in the HW set (problems 5.28, 5,40, 5.78, 5.80, 5.85,
and 5.92), so you are strongly encouraged to
complete this set before Exam 1.
4. Chan will give lectures until spring break
Test number
Test number
HITT RF Remote Login Procedure:
The radio channel number for this room is “07” (zero, seven).
It is STRONGLY recommended to login your remote for every class just
to be sure it is on the correct radio channel and working before class.
1.
2.
3.
4.
PRESS AND HOLD THE DOWN ARROW KEY until the
GREEN light on the remote turns RED.
PRESS THE “0” KEY and you will see the RED light flash
GREEN.
PRESS THE “7” KEY and you will see the RED light flash
GREEN.
PRESS AND RELEASE THE DOWN ARROW KEY again
and you will see the red light search for the receiver, if it
BLINKS GREEN MULTIPLE TIMES you are logged in.
1. A tortoise can run with a speed of 10.0 cm/s,
and a hare can run 20 times as fast. In a race, they
both start at the same time, but the hare stops to
rest for 4.0 minutes. The tortoise wins by a shell
(30 cm). What is the length of the race?
1.
2.
3.
4.
5.
7.2 m
1.3 m
25.2 m
0.3 m
0.1 m
Unknowns: d = length of race
t = time for tortoise
Vtortoise = d/t = 0.1
Vhare = (d-0.3)/(t-240) = 2
d - 0.3 = 2(t-240)
d – 0.3 = 2(d/0.1 – 240)
Clicker scores today will NOT count towards final grade.
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2. In Bosnia, the ultimate test of a young man's
courage used to be to jump (drop) off a 400 year old
bridge (now destroyed) into the River Neretva, 23 m
below the bridge. How fast was the jumper traveling
upon impact with the river?
1. 40.0 m/s
2. 23 m/s
Given: a, v0, ∆y, want vf
3. Need to know m
vf 2= vo2 + 2 a ∆y
4. 21.2 m/s
3. The driver of a truck slams on the brakes when he
sees a tree blocking the road. The truck slows down
uniformly with acceleration -5.6 m/s2 for 4.20 s,
making skid marks 58.9 m long that end at the tree.
With what speed does the truck then strike the tree?
Given: a, t, ∆x, want vf
1.
2.
3.
4.
Clicker scores today will NOT count towards final grade.
4. A track star in the broad jump goes into the jump at 12
m/s and launches himself at 20° above the horizontal.
How long is he in the air before returning to Earth?
1.
2.
3.
4.
0.42 s
0.84 s
1.26 s
1.68 s
1 Newton
5 Newtons
19 Newtons
39 Newtons
Any of the above
Directions are not given.
The three forces could add up
to a minimum of zero and a
maximum of 5 + 15 +20 = 40 N
Constant velocity == zero total
force
∆x = vo t + ½ a t2
then
use vf = vo + a t
5. A plane is moving due north, directly towards its
destination. Its speed in air is 200 mph. A constant
breeze is blowing from west to east at 30 mph. At
what speed is the plane moving north?
Clicker scores today will NOT count towards final grade.
1.
2.
3.
4.
5.
need to find vo first
Clicker scores today will NOT count towards final grade.
1.
2.
3.
4.
5.
6. Three forces, 5.0 N, 15.0 N, and 20.0 N, are
acting on a 9.81-kg object. Which of the following
forces could also be acting on the object if it is
moving with constant velocity?
58.9 m/s
2.28 m/s
5.60 m/s
4.20 m/s
217 mph
202 mph
198 mph
193 mph
183 mph
Clicker scores today will NOT count towards final grade.
7. Two forces are applied to a car in an effort to move
it, as shown in the figure. What is the resultant of
these two forces?
1.
2.
3.
4.
798 N, 8.8°
850 N, 0°
50 N, 180°
0N
30°
The magnitude of the fourth
force can range from 0 to 40 N
Clicker scores today will NOT count towards final grade.
Clicker scores today will NOT count towards final grade.
2
For objects connected
by a massless string
going over a
massless pulley:
1. Magnitude of
tension is the same
on both sides of the
pulley.
Atwood’s Machine
T1 = T2
T1
T2
a1 = a2
2. Magnitude of
acceleration is same
for both objects.
8. Two packing crates of masses m1 = 10.0 kg
and m2 = 3.50 kg are connected by a light
string that passes over a frictionless pulley as
in the figure. The 3.50 kg crate lies on a
smooth incline of angle 41.0°. Find the
acceleration of the 3.50 kg crate.
1.
2.
3.
4.
3.51 m/s2
4.10 m/s2
10.0 m/s2
5.59 m/s2
Clicker scores today will NOT count towards final grade.
9. Acceleration has dimensions of…
1.
2.
3.
4.
LT-1
LT2
LT-2
MLT-2
Clicker scores today will NOT count towards final grade.
10. A crate of mass 10.0 kg is pulled up a rough incline with an
initial speed of 1.50 m/s. The pulling force is 100 N parallel to the
incline, which makes an angle of 17.0° with the horizontal. The
coefficient of kinetic friction is 0.400, and the crate is pulled 4.85
m.
(a) How much work is done by gravity?
-139 J
(b) How much mechanical energy is lost due to friction?
182 J
(c) How much work is done by the 100 N force?
485 J
(d) What is the change in kinetic energy of the crate?
164 J
(e) What is the speed of the crate after being pulled 4.85 m?
5.92 m/s
Clicker scores today will NOT count towards final grade.
Good luck!
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