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Practice Midterm1
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Practice Midterm1
Due: 5:00pm on Wednesday, February 25, 2015
You will receive no credit for items you complete after the assignment is due. Grading Policy
Problem 3.43
Description: (a) If r_vec = bt^2 i_unit + ct^3 j_unit, where b and c are positive constants, when does the velocity
vector make an angle of 45.0 degree(s) with the x­ and y­axes?
Part A
∘
3^
If r ⃗ = bt2 ^
i + ct j , where b and c are positive constants, when does the velocity vector make an angle of 45.0
with the x­ and y­axes?
ANSWER:
t
= Problem 3.34
Description: (a) An aircraft performs a maneuver called an "aileron roll." During this maneuver, the plane turns like a
screw as it maintains a straight flight path, which sets the wings in circular motion. If it takes it v1 s to complete the
circle and the...
Part A
An aircraft performs a maneuver called an "aileron roll." During this maneuver, the plane turns like a screw as it
maintains a straight flight path, which sets the wings in circular motion. If it takes it 14 s to complete the circle and
the wingspan of the plane is 14.2 m, what is the acceleration of the wing tip?
ANSWER:
20 m/s 2
0.71 m/s 2
5.0×10−2 m/s 2
1.4 m/s 2
Exercise 3.26
Description: A model of a helicopter rotor has four blades, each of length L from the central shaft to the blade tip.
The model is rotated in a wind tunnel at a rotational speed of f. (a) What is the linear speed of the blade tip? (b)
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What is the radial...
A model of a helicopter rotor has four blades, each of length 3.60m from the central shaft to the blade tip. The model is
rotated in a wind tunnel at a rotational speed of 480rev/min .
Part A
What is the linear speed of the blade tip?
ANSWER:
v
= 181 m/s = Part B
What is the radial acceleration of the blade tip expressed as a multiple of the acceleration of gravity, g ?
ANSWER:
a
= 928 ⋅g = Exercise 4.20
Description: An astronaut's pack weighs w1 when she is on earth but only w2 when she is at the surface of an
asteroid. (a) What is the acceleration due to gravity on this asteroid? (b) What is the mass of the pack on the
asteroid?
An astronaut's pack weighs 10.1N when she is on earth but only 1.59N when she is at the surface of an asteroid.
Part A
What is the acceleration due to gravity on this asteroid?
ANSWER:
g
a
= = 1.54 m/s 2 Part B
What is the mass of the pack on the asteroid?
ANSWER:
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m
= = 1.03 kg Exercise 4.24
Description: The upward normal force exerted by the floor is 620 N on an elevator passenger who weighs 650 N. (a)
What is the magnitude of the acceleration? (b) What is the direction of the acceleration?
The upward normal force exerted by the floor is 620 N on an elevator passenger who weighs 650 N.
Part A
What is the magnitude of the acceleration?
ANSWER:
a
= 0.452 m/s 2 Part B
What is the direction of the acceleration?
ANSWER:
upward
downward
Problem 3.65
Description: A snowball rolls off a barn roof that slopes downward at an angle of 40 degree(s) . The edge of the roof
is 14.0 m above the ground, and the snowball has a speed of 7.00 m/s as it rolls off the roof. Ignore air resistance.
(a) How far from the...
A snowball rolls off a barn roof that slopes downward at an angle of 40 ∘ . The edge of the roof is 14.0 m above the
ground, and the snowball has a speed of 7.00 m/s as it rolls off the roof. Ignore air resistance.
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Part A
How far from the edge of the barn does the snowball strike the ground if it doesn't strike anything else while falling?
ANSWER:
x
= 6.93 m Part B
Draw x − t graphs for the motion in part A.
ANSWER:
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Part C
Draw y − t graphs for the motion in part A.
ANSWER:
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Part D
Draw v x
−t
graphs for the motion in part A.
ANSWER:
Part E
Draw v y
−t
graphs for the motion in part A.
ANSWER:
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Part F
A man 1.9 m tall is standing 4.0 m from the edge of the barn. Will he be hit by the snowball?
ANSWER:
Yes
No
Problem 2.35
Description: (a) A toy rocket is launched vertically from ground level (y = 0.00 m), at time t = 0.00 s. The rocket
engine provides constant upward acceleration during the burn phase. At the instant of engine burnout, the rocket has
risen to v1 m and acquired a...
Part A
A toy rocket is launched vertically from ground level (y = 0.00 m), at time t = 0.00 s. The rocket engine provides
constant upward acceleration during the burn phase. At the instant of engine burnout, the rocket has risen to 49 m
and acquired a velocity of 60 m/s. The rocket continues to rise in unpowered flight, reaches maximum height, and
falls back to the ground with negligible air resistance. The speed of the rocket upon impact on the ground is closest
to
ANSWER:
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76 m/s
68 m/s
82 m/s
62 m/s
55 m/s
Problem 3.30
Description: (a) A cart is moving with a constant horizontal velocity of 5.00 m/s. A small pebble is launched from
the front of the cart with a velocity of 8.00 m/s at 60.0° above the horizontal as measured relative to the cart (see
figure) and experiences no...
Part A
A cart is moving with a constant horizontal velocity of 5.00 m/s. A small pebble is launched from the front of the
cart with a velocity of 8.00 m/s at 60.0° above the horizontal as measured relative to the cart (see figure) and
experiences no significant air resistance. Just as the pebble returns to the level from which it was launched, its
distance from the front of the cart is closest to
ANSWER:
9.19 m.
4.60 m.
5.66 m.
11.3 m.
2.83 m.
Exercise 3.19
Description: In a carnival booth, you win a stuffed giraffe if you toss a quarter into a small dish. The dish is on a
shelf above the point where the quarter leaves your hand and is a horizontal distance of 2.1 m from this point (the
figure ). If you toss the coin ...
In a carnival booth, you win a stuffed giraffe if you toss a quarter into a small dish. The dish is on a shelf above the point
where the quarter leaves your hand and is a horizontal distance of 2.1 m from this point (the figure ). If you toss the coin
with a velocity of 6.4 m/s at an angle of 60 ∘ above the horizontal, the coin lands in the dish. You can ignore air
resistance.
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Part A
What is the height of the shelf above the point where the quarter leaves your hand?
Express your answer using two significant figures.
ANSWER:
H
= 1.5 m Part B
What is the vertical component of the velocity of the quarter just before it lands in the dish?
Express your answer using two significant figures.
ANSWER:
vy
= ­0.89 m/s Exercise 4.32
Description: A skier of mass 65.0 kg is pulled up a snow­covered slope at constant speed by a tow rope that is
parallel to the ground. The ground slopes upward at a constant angle of 26.0 degree(s) above the horizontal and you
can ignore friction. (a) Calculate...
A skier of mass 65.0 kg is pulled up a snow­covered slope at constant speed by a tow rope that is parallel to the
ground. The ground slopes upward at a constant angle of 26.0 ∘ above the horizontal and you can ignore friction.
Part A
Calculate the tension in the tow rope.
ANSWER:
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T
= 279 N Copyright © 2015 Pearson. All rights reserved.
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