2. (2 Points) Explain why an object that is shot horizontally and an item that is dropped
from rest, when starting at the same height, hit the ground at the same time.
3. (2 Points) Describe why an object can have constant speed yet changing velocity, but
not the other way around. Give an example to support your answer.
4. (2 Points) What would it mean for data to have high accuracy but low precision?
5. (2 Points) If you have a cube of Gold, with volume V=5 cm’, what is the mass of the gold
you have? The density of gold is 19.32 g/cm’.
Work Out: For the following questions, show all calculations for full credit.
m
m
т
+
given by i
6. (10 Points) The velocity of Chance (the ever-loving albino pitbull) running in a park is
vč(t) = [0.48″* +(0.74″))}]î +[(0.33%)**]j.
a) What are rä(t) and ry(t), the x- and y-components of the position of Chance, as
functions of time? Assume an initial position of (0,0).
+
b) What is the acceleration (in unit vector notation) of Chance, with respect to time?
m
m
c) Chance’s dog friend Waffles is chasing after Chance. If Waffles has a velocity given by
1
the equation
what is Waffle’s velocity
relative to Chance? Give your answer in unit-vector notation.
vū(t) = [0.00″ + (0.82″))t]i + [(0.39%)*]j.
1
7. (10 Points) The following plot shows the velocity of an object, with respect to time.
Problem 7
Velocity (m/s)
-2
0
2
4
6
8
10
(s)
a) At what time(s) does the object change direction?
b) What is the distance travelled of the object at t=9 seconds?
c) What is the displacement of the object at t=9 seconds?
d) At what time(s) is the acceleration negative?
8. (10 Points) Vin, an allomancer (e.g. magic-y person) from the Mistborn trilogy, has a
number of innate powers. One of these is the ability to push or pull on metals from a
distance. Say that Vin sees an enemy allomancer on a balcony. The building is 8.0
meters horizontally from her, and the balcony is 6.0 meters high. She grabs a metal coin,
and from a height of 1.0 meters above the ground, pushes (launches) the coin at the
allomancer. The enemy allomancer, sensing the shot, drops straight down from the
balcony the instant the coin launches. Ignore air resistance.
a) At what angle is Vin initially shooting at?
Initial Trajectory
“Not drawn
to scale
Actual Trajectory
6 m
8 m
1 m
b) If the coin initially travels along that angle at 30.0
m/s, how much time passes between the coin being
pushed and it arriving at the building?
c) How far will the enemy allomancer fall in the time found above? Ignore air resistance,
and treat the enemy allomancer as being in free fall.
d) At what height will the coin hit the building? Does Vin hit her target?
9. (10 points) Arya, my little black and white cat, has a giant hamster wheel she runs on.
Assume she starts from rest, and the wheel rotates on perfectly frictionless supports.
The wheel’s inner diameter is 1 meter.
a) If Arya accelerates the wheel at a constant angular acceleration of 7.5 rad/s2 for 3
seconds, what is the final angular speed of the wheel?
d) At what height will the coin hit the building? Does Vin hit her target?
9. (10 points) Arya, my little black and white cat, has a giant hamster wheel she runs on.
Assume she starts from rest, and the wheel rotates on perfectly frictionless supports.
The wheel’s inner diameter is 1 meter.
a) If Arya accelerates the wheel at a constant angular acceleration of 7.5 rad/s2 for 3
seconds, what is the final angular speed of the wheel?
b) What is Arya’s tangential speed, in relation to the hamster wheel, after the 3 seconds?
c) What is Arya’s centripetal acceleration, when running at full speed on the bottom of
the hamster wheel?
Extra Credit: The following question is for extra credit. A total of up to 5 points can be earned.
Explain why two objects of different mass hit the ground at the same time in a vacuum chamber.
What parameters are missing in a vacuum chamber?
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