Reading Quiz

Question 1:

Answer:

1. A bicycle tends to automatically steer itself in the direction it is leaning which provides dynamic stability. The automatic steering is produced by two things: one being gyroscopic precession, which causes the wheel's rotational axis to pivot when the pavement's upward support force produces a perpindicular torque on the wheel (this happens when the bicycle leans to one side while moving). Also if the front wheel touches the ground behind the steering axis, this provides stability since the front wheel will naturally steer in the direction the bicycle is leaning so as to lower is center of gravity and potential energy.
3. One of the key features that contributes to a bicycle's dynamic stability is the fact that the wheels behave as gyroscopes spinning at a constant angular speed. Since a wheel's angular momentum can be changed only by a torque, it tends to keep its upright orientation. The other key feature is that the bicycle corrects itself automatically by way of gyroscopic precission.
4. Dynamic Stability is stability in motion. A moving bicycle is very stable because of its tendency to steer automatically in whatever direction it's leaning. It drives under the combined center of mass and returns to that unstable equilibrium.
5. Dynamic stability means stability in motion, and bicycles are able to steer automatically. If the rider leans to one side or the other, the bike will turn in that direction. The fact that the wheels behave as gyroscopes also contributes to dynamic stability. As the bike moves forward, its acceleration allows it to remain upright and beat the force of gravity pulling downward on either side.
6. The dynamic stability of a bicycle results from its automatic steering effect, which causes it to steer in whatever direction it leans. This tendency involves the wheels, which act as gyroscopes. The angular momentum of the wheels causes the automatic steering effect by gyroscopic precession, in which the rotational axis of the front wheel pivots as a result of a torque that is exerted perpendicular to the angular momentum. In order for this to take place and the bike to be "ridable," the front wheel of the bicycle must touch the ground behind the steering axis.
7. The wheels act as gyroscopes, so they're always trying to restore themselves to their equilibrium position. Also, since they are statically unstable they can lean while they are in motion to maintain their equilibrium.
8. The wheels act as gyroscopes when spinning. The wheels have angular momentum and the only way to change its momentum is by applying a torque. Because of this, it tends to stay up when the wheels are spinning. Also the shape and angle of the fork allow the bicycle to have dynamic stability. If the shape and angle of the fork allow the wheel to touch the ground behind the steering axis, the bicycle is dynamically stable.
9. Dynamic stability is stability in motion. What makes it stable is the angular momentum of the spinning wheels which keep spinning along a fixed axis in space. Secondly, gyroscopic precession also helps.
10. A bicycle has dynamic stability, meaning it is very stable when it is in motion as a result of two main effects. First the wheels act like gyroscopes, which means that the wheel's angular momentum causes it to tend to continue rotating at a constant angular speed about its fixed axis. WHen torque is applied to the wheel, its axis pivots to maintain its upright position. The other thing that contributes to a bicycle's dynamic stability is the shape and angle of the fork that supports its front wheel. The fork causes the wheel to touch the ground in a certain location so that when the bike leans its center of gravity can be lowered by turning the bike in that direction.
11. Gyroscopes - The angular momentum of the wheels spinning means that they should not tip unless a torque acts upon them. Also, ensuring that the wheel is in a certain position relative to the front fork steers the bike in the direction the bike is leaning rather than tipping over. These both contribute to its dynamic stability, or its stability in motion.
12. the gyroscope effect from the wheels means that the wheels have angular momentum, which is a vector, and can only be changed by a torque, so the wheels tend to stay in their path unless acted upon by a torque. Also, when the wheels are spinning and tilt for the bike to turn, the pavement exerts a perpendicular torque on the wheel, which brings the wheel toward the direction it tilts and helps you turn.
13. the gyroscope effect from the wheels means that the wheels have angular momentum, which is a vector, and can only be changed by a torque, so the wheels tend to stay in their path unless acted upon by a torque. Also, when the wheels are spinning and tilt for the bike to turn, the pavement exerts a perpendicular torque on the wheel, which brings the wheel toward the direction it tilts and helps you turn.
14. One thing that contributes to dynamic stability is teh angular momentum that teh wheel's have. Because they have angular momentum, they tend to keep an upright orientation. Another thing that contributes to the dynamic stability is the gyroscopic precesion. When the bycicle leans to one side, the upward force of the ground produces a perpendicular torque on the wheel and makes the wheel rotate towards the way it is leaning.
15. Since a spinning wheel has a angular momentum that can only be changed by torque it tends to keep an upright position. It is also dynamically stable because of gyrosopic precision. When the torque makes the wheel precess the force from the ground makes the axis of rotation pivot to the left and make the bicycle stable.
16. Some key features that contribute to a bicycles dynamic stability is that the bicylce is an unstable equilibrium.
17. The bicycle will steer in whatever direction it is leaning, so it can return to equilibrium. Also, because of the shape and angle of the fork supporting the wheel, the bike is able to lower the center of gravity and its potential energy.
18. The key features are the position of the center of mass, the torque on the wheels experiences once the wheel is no longer perpendicular to the ground, and the axis of rotation of the front wheel. In order for the bicycle to have dynamic stability, the axis of rotation needs to be positioned correctly, and the bike tires need to be able to lean and experience both a torque and a support force.
19. A bicycle's dynamic stability is based on it's tendency to steer automatically in whatever direction it's leaning. This is based on its rotation and potential energy. The moving wheels have angular momentum which can only be changed by a torque (leaning). When the bicycle is upright and heading straight the support force points directly up for a zero net force, and as the wheel leans the frictional force points in the direction the bike is leaning and helps to maintain this equilibrium.
20. A bike has the natural tendency to steer under the combined center of mass and always return to an unstable equilibrium. A bike steers automatically by gyroscopic precession. It can also lean, which balances the frictional torque and thus keeps it upright. By having the wheels and pedals move at different speeds, it is easier for the rider to choose how to exert forces on the pedals to gain different speeds.
21. The first is that a bicycle has factors that produce an automatic steering effect. The first is that the wheels act as gyroscopes which means that it has angular momentum which tends to conintinue constantly around a fixed axis, this help keep it standing. In addition to this the torque generated when a bike turns helps keep it up. There is also an energy aspect that has an effect, because of thedesign of the fork supported by the front wheel, the bike automatically steers in the direction that it is leaving, this happens because it is the fastest way that the bike can lower its potential energy.
22. Dynamic Stability is an objects stability when it is in motion. A bicycle's has incredible dynamic stability and it is so good that it is almost hard to tip over and can even be ridden without any hands on the handlebars. This dynamic stability results from its tendency to steer automatically in whatever direction it's leaning. A foward moving bike naturally drives under the combined center of mass and returns to its unstable equilibrium. The bike is also stable when it moves becuase its front wheel touches the ground behing the steering axis and as a result the front wheel naturally steers in the direction that the bike is leaning and returns the bike to its upright position.
23. A moving bicycle remains upright with the help of two stabilizing effects of motion. One due to gyroscopic precession and the other due to the shape and angle of the front fork. These effects work together to steer the bicycle in the direction that it's leaning. Whenever it tips, it automatically drives under its center of gravity and returns to upright. Leaning is also an essential part of turns. By leaning properly during a turn, the bicyclist ensures that there is not overall torque on the bicycle and that it doesn't tip over.
24. Its center of gravity, its weight, its pivot, and its torque about the pivot.

Question 2:

Answer:

1. Newton's third law of motion is a key principle behind rocket propulsion: the equal and opposite force pair includes the force of the rocket pushing its exhaust backward and the force of the exhaust pushing the rocket forward.
3. The key physics principle is Newton's 3rd law of motion that for every action there is an opposite and equal reaction.
4. Uses a chemical reaction to create very hot exaust gas. Potential energy becomes thermal energy. The thermal energy is largely kinetic energy hidden in the motion of the tiny molecules. The engine steers most of this in one direction and the engine obtains thrust in the opposite direction.
5. Newton's Third Law- for every force there is an equal and opposite reaction force. Hot exaust gas in the de Laval nozzle creates a chemical reaction that produces a force that propels the rocket against the force of gravity and into the air.
6. Newton's third law is important--for every action, there is an equal and opposite reaction. Also key is the law of conservation of momentum.
7. The rocket gains momentum in one direction by pushing out fast-moving molecules in the opposite direction. The fast-moving molecules are pushed out through a nozzle so that they give the rocket some direction.
8. Newton's Third Law because the rocket ejects gass from its tail end. The nozzle allows the gas to be pushed out with a very high velocity. This gas will push hard on the rocket, and the rocket will push just as hard on it.
9. Newton's third law. When an object exerts a force on something, there is an equal and opposite force exerted on the original object.
10. The most important physics principle behind rocket propulsion is Newton's 3rd Law, which states that for every force one object exerts on another, that second object exerts a force equal in magnitude but opposite in direction on the first object. In terms of a rocket this means that a rocket's thrust is the force equal and opposite to the force the rocket exerts on its fuel in expelling it. As the rocket pushes its fuel (in the form of exhaust) out, that exhaust pushes back on the rocket in the opposite direction which is up. This therefoe propels the rocket into space.
11. Newton's 3rd law, that every force has an equal and opposite force. By pushing off of its own fuel, a rocket and achieve acceleration even in space where there's nothing else to push off of.
12. Thrust: When the chemical reaction in the rocket's engine produces hot gas, which has much kinetic energy. This gas exits the back of the rocket, and according to Newton's third law, there is an equal and opposite reaction, so the rocket is pushed foward, opposite the gas.
13. Thrust: When the chemical reaction in the rocket's engine produces hot gas, which has much kinetic energy. This gas exits the back of the rocket, and according to Newton's third law, there is an equal and opposite reaction, so the rocket is pushed foward, opposite the gas.
14. The key physics principle behind rocket propulsion is that by it forcing gas away from the rocket itself, that creates an equal and opposite force that pushes the rocket forward. The rocket does not need to push off of anything in order to acclerate forward.
15. Newton's third law - that describes when you push on an object it pushes back on you with an equal but opposit force
16. The key physics principle behind rocket propulsion is a trust force.
17. Conservation of momentum - the rocket propels the gas outward, so the gas exerts a force to propel the rocket forward.
18. The key principle is Newton's third law. The thrust force created by the potential energy of fuels on the rocket causes an equal and opposite reaction. If the momentum of the fuels is sent in one direction, conservation of momentum requires that the rocket move in the other direction.
19. A rocket is propelled by thrust. It turns potential energy in chemicals into thermal energy- random particles moving quickly. The exhaust directs the random motion of thermal energy in a single direction which creates kinetic energy. This pushes the rocket in the opposite direction based on the principles of equal and opposite forces and maintainence of momentum.
20. Newton's Third Law of Motion: for every action, there's an equal and opposite reaction.
21. The physics principle is Newton's 3rd law, or perhaps more specifically conservation of momentum.
22. Thrust is the principle behind rocket propulsion.
23. A rocket has a thrust force. This is when gas is ejected from an engine and the rocket pushes on the gas and the gas pushes back. The rocket's thrust is used to lift the rocket against the force of gravity and to accelerate it upward.
24. The rocket pushes exhaust backward and the exhaust is pushing the rocket forward. These are two equal but opposite forces, illustrating Newton's 3rd law.

Question 3:

Answer:

1. I was confused by the discussion of gas and rocket propulsion, how energy is potential energy in the stored chemical fuel, then thermal energy in the exhaust gas and kinetic energy to move the rocket: how does the nozzle convert thermal energy into kinetic energy directed away from the rocket engine.
3. I'd like to spend more time on the dynamic stability of bicycles versus tricycles because I found that whole section confusing.
4. could we go over the idea of rocket propulsion again.
5. None :)
6. The chapter about rockets was kind of confusing, particularly the part about propulsion--while I think I understand the basic concept, it was easy to get lost on some of the details.
7. I need some clarification on how the tricycle is more prone to fall over around a turn than a bike, and how leaning on the bike makes it possible to make almost any turn. Why doesn't the bike fall over?
8. I don't get how you can steer a bicycle without using the handlebars.
9. i'm kind of confused about gyroscopic precession
10. I understood these sections in the text.
11. I think I have it all under control.
14. I still find the reason that the bycicle wheel requires force to move it off of the axis it curently is, a little confusing. I'm not sure why this happens or the forces or principles that make this happen. I would like to further discuss this in class if possible.
15. I found the stuff about gyroscopic presicion and how bikes are dynamically stable, difficult to understand.
16. could you possibly go over the bicycle and why it is so unstable. Also, How would a unicyle work?
17. The nozzle shape and its effect on propulsion
18. the way the bike works is still a little confusing
19. bicycle steering. The force diagram is a little confusing.
20. How does the rear wheel of the bike work exactly? Bit confused with that.
21. I would like to hear you explain the way a bike works.
22. the idea of thrust and how a bike stands up straight even when pushed.
23. I don't understand how friction can sometimes be considered a torque when looking at bicycles.
24. none

Question 4:

Answer:

1. I know we have discussed the feeling of acceleration, but can we talk about what it means to experience different feelings of acceleration, varying in strength or direction, for example a 1g versus a 5g feeling of acceleration.
3. Nothing that I can think of.
4. nothing at this time.
5. None
6. After doing the lab yesterday, I realized I am still a little confused about the concept of momentum, and how it's different from inertia.
8. nothing
9. --
10. I think I'm okay with everything as of now.
11. Still hangin in there.
14. I think I have a firm grasp on all material from previous classes.
15. some of the stuff from the lab about torque and force involving the wheel when you try to turn it
16. I dont have any questions or problems with work from previous classes
17. None.
18. -
19. none
20. Past class material is clear. The lab was awesome, and clarified things even more.
21. Nothing really. Thanks
22. elastic PE
23. I'm still a little confused with angular momentum and angular impulse.
24. none