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Course: American System Physics
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American System Physics

A Physics Toolkit

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Representing Motion

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Accelerated Motion

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Forces in One Dimension

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Displacement and Force in Two Dimensions

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Motion in Two Dimensions

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Gravitation

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Rotational Motion

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Momentum and Its Conservation

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Energy and Its Conservation

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Thermal Energy

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States of Matter

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Vibrations and Waves

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Sound

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Fundamentals of Light

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Reflection and Refraction

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Interference and Diffraction

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Electrostatics

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Electric Current and Circuits

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Magnetic Fields

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Electromagnetic Induction and Electromagnetism

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Quantum Theory and the Atom

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Solid-State Electronics

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Nuclear and Particle Physics

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Quiz

9.3 Momentum in Two Dimensions and Rockets – Quiz

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Momentum in Two Dimensions and Rockets American Physics quiz: free practice for American System Physics. Work through this Momentum in Two Dimensions and Rockets American Physics quiz and get instant feedback on every answer. If you get stuck, review the 9.3 Momentum in Two Dimensions and Rockets — Notes lesson. More practice: American System Physics — all units. Syllabus: OpenStax free science textbooks.

  • Questions count: 50
  • Passing grade: A-
  • Time limit:
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1.
The diagram shows the x- and y-components of a ball's momentum. What is the magnitude and direction of its momentum?
Dr Dabour Hub Academy - figure 1
14 kg·m/s at 45° above the +x axis
10 kg·m/s at 37° above the +x axis
10 kg·m/s at 53° above the +x axis
2.0 kg·m/s at 37° above the +x axis
2.
Toy car A (3.0 kg, 4.0 m/s east) and toy car B (2.0 kg, 3.0 m/s north) collide at a junction and stick. Their momenta are shown. What is their velocity just after?
Dr Dabour Hub Academy - figure 2
3.6 m/s at 45° north of east
2.7 m/s at 63° north of east
2.7 m/s at 27° north of east
13 m/s at 27° north of east
3.
The vector diagram is for a glancing collision. What is the magnitude of B's momentum after the collision?
Dr Dabour Hub Academy - figure 3
6.7 kg·m/s
6.0 kg·m/s
5.0 kg·m/s
10 kg·m/s
4.
An object at rest breaks into three pieces. The momenta of two pieces are shown (in kg·m/s). What is the momentum of the third piece?
Dr Dabour Hub Academy - figure 4
17 kg·m/s, pointing down and to the left
13 kg·m/s, pointing down and to the left
13 kg·m/s, pointing up and to the right
7.0 kg·m/s, pointing down and to the left
5.
The graph shows lab data for a spinning platform with no external torque. What does the gradient represent, and what is its value?
Dr Dabour Hub Academy - figure 5
The moment of inertia, about 1.9 kg·m²
The angular impulse, about 0.5 N·m·s
The angular momentum, about 1.9 kg·m²/s
The torque, about 1.9 N·m
6.
Use the graph. What is the skater's moment of inertia after pulling her arms in?
Dr Dabour Hub Academy - figure 6
8.75 kg·m²
2.1 kg·m²
0.71 kg·m²
1.4 kg·m²
7.
The graph shows the mass of a rocket during a burn. The exhaust speed is constant at 2400 m/s. What is the thrust?
Dr Dabour Hub Academy - figure 7
1.2 × 10^5 N
2.4 × 10^5 N
7.2 × 10^6 N
2400 N
8.
The measured momenta (kg·m/s) for a glancing collision are shown. Which conclusion is best supported?
Dr Dabour Hub Academy - figure 8
Both components are exactly conserved
y-momentum is not conserved because both pucks move off at angles
y-momentum is conserved, but about 11% of the x-momentum is lost, probably to friction
x-momentum increased, so an external force pushed the pucks
9.
A student on a rotating stool moves hand weights inwards, and I and ω are estimated for each position. Which result is anomalous?
Trial 1
Trial 4
Trial 2
Trial 3
10.
A lump of clay is dropped onto a spinning turntable. Using the table, what is the new angular velocity?
37.5 rad/s
30 rad/s
6.0 rad/s
24 rad/s
11.
Momentum components for two pucks were found from a video of a glancing collision (B was at rest). What is the missing y-component for B after the collision?
−0.36 kg·m/s
+0.36 kg·m/s
0 kg·m/s
−0.24 kg·m/s
12.
The table shows a skater's moment of inertia in three positions. In position 1 she spins at 2.0 rad/s. How fast does she spin in position 3?
0.67 rad/s
6.0 rad/s
4.0 rad/s
3.0 rad/s
13.
An object at rest explodes into three fragments. Using the table, what is fragment C's momentum?
(2.0, 5.0) kg·m/s
(−8.0, 1.0) kg·m/s
(−2.0, −5.0) kg·m/s
(0, 0) kg·m/s
14.
Which engine in the table produces the greatest thrust?
Engine P
Engine Q
Engine R
Engine S
15.
Identical steel pucks (one at rest) are made to collide. The table gives the angles each puck moves off at, measured either side of the original line. Which trial is closest to an elastic collision?
Trial 2
Trial 1
Trial 3
Trial 4
16.
Two carts collide on a smooth floor and stick. Using the table, what is their speed just after the collision?
3.3 m/s
1.7 m/s
7.2 m/s
2.4 m/s
17.
A puck has momentum 12.0 kg·m/s directed 30° above the +x axis. What is its x-component of momentum?
10.4 kg·m/s
6.00 kg·m/s
12.0 kg·m/s
13.9 kg·m/s
18.
A 1.5 kg puck moving at 4.0 m/s along +x strikes a stationary 2.5 kg puck. Afterwards the 1.5 kg puck moves at 1.0 m/s along +y. What is the velocity of the 2.5 kg puck?
2.5 m/s at 14° above the +x axis
2.4 m/s along +x
3.0 m/s at 14° below the +x axis
2.5 m/s at 14° below the +x axis
19.
A rocket engine expels 40 kg of exhaust gas per second at 2500 m/s. What is the thrust?
62.5 N
2540 N
1.0 × 10^5 N
1.25 × 10^8 N
20.
In deep space a rocket's engine gives a constant thrust of 1.0 × 10^5 N. How does its acceleration change as its mass falls from 20 000 kg to 12 000 kg?
It stays at 5.0 m/s²
It falls from 8.3 m/s² to 5.0 m/s²
It rises from 0.20 m/s² to 0.12 m/s²
It rises from 5.0 m/s² to 8.3 m/s²
21.
A 50 kg probe at rest in space ejects 0.50 kg of gas backwards at 800 m/s in one short burst. What speed does the probe (now 49.5 kg) gain?
8.1 m/s
8.0 m/s
400 m/s
0.031 m/s
22.
A skater spins at 1.5 rev/s with moment of inertia 5.0 kg·m². She pulls her arms in until her moment of inertia is 2.0 kg·m². What is her new rate of spin?
0.60 rev/s
3.75 rev/s
1.5 rev/s
7.5 rev/s
23.
A diver reduces her moment of inertia from 14 kg·m² to 4.0 kg·m² by tucking. By what factor does her angular velocity change?
It decreases by a factor of 3.5
It increases by a factor of 10
It increases by a factor of 3.5
It stays the same
24.
A net torque of 2.5 N·m acts for 4.0 s on a wheel of moment of inertia 0.50 kg·m², initially at rest. What is its final angular velocity?
10 rad/s
5.0 rad/s
1.25 rad/s
20 rad/s
25.
A flywheel has moment of inertia 0.20 kg·m² and spins at 15 rad/s. What is its angular momentum?
3.0 kg·m²/s
3.0 kg·m/s
75 kg·m²/s
22.5 kg·m²/s
26.
Pucks on an air table are filmed from above to study a 2-D collision. Why is a ruler placed in the camera's view?
To reduce friction on the pucks
To give a length scale so distances in the video can be converted to metres
To keep the collision one-dimensional
To measure the mass of each puck
27.
A student measures the velocities of two pucks before and after a glancing collision. Which method correctly tests conservation of momentum?
Add the magnitudes of the momenta before and compare with the sum after
Compare the total speeds before and after
Resolve every momentum into x- and y-components and compare the totals in each direction separately
Check only the direction of motion of the faster puck
28.
Linear and angular momentum are each changed by a different kind of impulse; a student pairs each quantity with its cause of change. Which pairing is correct?
Linear momentum — changed by angular impulse τΔt
Angular momentum — changed by angular impulse τΔt
Angular momentum — changed by impulse FΔt only
Linear momentum — conserved when net external torque is zero
29.
For each spinning athlete or object, a prediction is made about moment of inertia and rate of spin. Which pairing is correct?
Skater spreads arms — I decreases, ω increases
Star collapses — I increases, ω decreases
Diver tucks — I decreases, ω increases
Diver opens out — I decreases, ω decreases
30.
A rocketry formula sheet lists quantities next to equations. Which pairing is correct?
Resultant momentum — px + py
Angular momentum — mv²
Angular impulse — I/ω
Thrust — (Δm/Δt) × v_exhaust
31.
For a momentum p at angle θ above the x-axis, the y-component is p_y = _____.
p sin θ
p cos θ
p tan θ
p/sin θ
32.
A rocket must produce a thrust of 3.0 × 10^6 N with an exhaust speed of 2000 m/s. It must expel gas at _____.
6.0 × 10^9 kg/s
1500 kg/s
0.00067 kg/s
150 kg/s
33.
A wheel spinning at 2.0 rev/s has an angular velocity of _____.
2.0 rad/s
6.28 rad/s
12.6 rad/s
0.32 rad/s
34.
The rotational equivalent of linear momentum is angular momentum, L = _____.
mv
τΔt
½Iω²
Iω
35.
A momentum with components p_x = 5.0 kg·m/s and p_y = 5.0 kg·m/s points at _____ to the x-axis.
45°
30°
60°
90°
36.
In a two-dimensional collision, the x-momentum and the y-momentum of a closed, isolated system are each conserved separately. True or false?
False
True
False, only the total magnitude is conserved
True only if the collision is elastic
37.
A rocket needs air behind it to push against in order to accelerate. True or false?
True
True, which is why rockets cannot work in space
False
True only during launch
38.
The thrust on a rocket equals the mass of gas expelled per second multiplied by the exhaust speed. True or false?
False
False, it equals the rocket's mass times the exhaust speed
True only in the atmosphere
True
39.
For a constant thrust, a rocket's acceleration increases as its fuel is used up. True or false?
True
False
False, the acceleration stays constant
False, the acceleration decreases
40.
An ice skater who pulls her arms in spins more slowly. True or false?
True
False
True, because her moment of inertia decreases
True only on rough ice
41.
The SI unit of angular momentum is kg·m/s. True or false?
True
True, the same as linear momentum
False
True only for rigid objects
42.
When a moving puck makes an elastic glancing collision with an identical puck at rest, the two pucks move off at 90° to each other. True or false?
False
False, they move off along the same line
True only if the collision is perfectly inelastic
True
43.
After a glancing collision with a stationary target, the y-components of the two objects' momenta are equal in size and opposite in direction. True or false?
True
False
False, both must move above the original line
True only for equal masses
44.
The angular momentum of a system changes only when a net external torque acts on it. True or false?
False
True
False, internal forces also change it
True only for spinning stars
45.
A diver opens out her body before entering the water to slow her rotation. True or false?
False
False, opening out makes her spin faster
True
True only if she is falling slowly
46.
The magnitude of a momentum vector is found by adding its x- and y-components. True or false?
True
True, because momentum is additive
True only when the components are equal
False
47.
A collapsing star can end up spinning many times per second because its moment of inertia decreases enormously. True or false?
True
False
False, collapse makes stars spin slower
True only if an external torque acts
48.
A spinning bicycle wheel tends to keep the direction of its axis because of conservation of angular momentum. True or false?
False
True
False, it is due to friction at the hub
True only if the wheel is not spinning
49.
Timing ten rotations of a turntable and dividing by ten gives a smaller percentage uncertainty in the period than timing one rotation. True or false?
False
False, the uncertainty is ten times larger
True
True only with a light gate
50.
A rocket gains forward momentum equal in size to the backward momentum given to its exhaust gases. True or false?
False
False, the rocket gains kinetic energy only
True only when the rocket is on the launch pad
True
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