Chapter 8 Review

Video Review

Key Concept Summary

TA Summary

Vocabulary

Any quantity that remains constant.

The process by which carbon is transferred through the atmosphere to living organisms and back to the atmosphere.

Obtained by adding the number of protons to the number of neutrons.

An object's mass times its velocity.

An object's mass times its speed times its distance from the center of its orbit.

Small, unbreakable constituents of matter.

True/False

All physical objects must obey a general law of conservation of mass.

True False

Atoms are conserved in mechanical and chemical processes.

True False

Protons and neutrons are fundamental particles.

True False

Electron-like particles are considered to be fundamental particles.

True False

Atomic mass number is always conserved.

True False

Neutrons, protons, and electrons are all charged particles.

True False

Electrons can easily be transferred from one object to another.

True False

Scuffing across the carpet with your tennis shoes creates charge that didn't previously exist.

True False

The motion of a single object subject to no net forces is conserved.

True False

Particles moving at high speeds require less force to accelerate than slower identical particles.

True False

Linear momentum is the speed at which an object moves.

True False

Analysis

At low speeds, mass can

transfer from one object to another. change its total amount. both the first and second choices

Which of the following quantities remain(s) constant in the Carbon Cycle?

total amount of carbon dioxide total number of carbon atoms total mass all of the above the second and third choices above

Angular momentum depends on which of the following?

the mass of the object how fast it's moving how far it is from the center of rotation all of the above the first two choices above none of the above

A wannabe superhero sits on a frictionless hoverboard while holding a fire extinguisher (his means of propulsion). This person fires the extinguisher to the left. What direction does the hoverboard travel?

right left it will remain stationary

Suppose the same person, on the same hoverboard, still holding the extinguisher, decides to refill the fire extinguisher. He attaches a long hose running from a compressor into the extinguisher. The air is travelling horizontally right to left when it enters the extinguisher. What direction will the cart move (until he runs out of compressor hose)?

right left it will remain stationary

A figure skater pulls her arms in as she spins during a jump. What happens to her angular momentum?

It increases. It decreases. It will remain the same.

For the next two questions consider the following situation. A lucky college student wins a five minute free shopping spree at a local super market. He gets to take home all the groceries that he can get into a shopping cart in 5 minutes. In preparation, he checks out the carts in advance. He finds a shopping cart with frictionless wheel bearings that also rolls straight. When he gives this perfect shopping cart a hard push at the beginning of the aisle, it rolls at constant speed all the way to the end. On the day of the big event, he gives the cart a hard push and runs along side it dropping groceries in with both hands.

As mass is added to the cart, what happens to its speed?

It increases. It decreases. It remains constant.

As mass is added to the cart, what happens to its (just the cart's) energy?

It increases. It decreases. It remains constant.

In a car accident are the passengers better off if the cars stick together or if they bounce off of each other?

Stick together. Bounce off of each other. It makes no difference

The Earth has a slightly elliptical orbit. It is closest to the sun in December, and farthest from the sun in June. As the Earth gets closer to the sun, what happens? (Select all correct answers.)

The Earth spins faster, making the days shorter. It orbits about the sun faster. (Its angular speed increases.) Nothing about either its spin or orbital motion changes

The next two questions refer to the following situation: A diver wishes to complete a double back tuck dive. In this dive he leaves the board, pulls his legs up to his chest bent at the knees, completes 2 revolutions, and straightens his body for another 1/2 revolution before he enters the water.

When does a diver have the largest angular momentum?

Immediately after leaving the board When his legs are pulled up to his chest When he is stretched out just before entering the water His angular momentum is virtually constant throughout the dive.

When does the diver have the largest angular velocity?

Immediately after leaving the board When his legs are pulled up to his chest When he is stretched out just before entering the water His angular velocity is virtually constant throughout the dive.

In a car crash, it is not uncommon for the cars to spin after the impact even though they were moving in straight lines before the impact. Which is the most correct explanation for this observation?

In a collision only linear momentum is conserved, angular momentum is not. In a collision if one car spins clockwise, the other will spin counter clockwise, and the total angular momentum is zero. In a collision the tires stop spinning and the angular momentum of the tires is transferred to the rest of the vehicles. Both angular and linear momentum are conserved. In an off center collision, the angular momentum is not zero to start with because the car that hits off center has mass, velocity, and a radius from the center, regardless of the fact the cars are moving in a straight line.

In a game of crack the whip, skaters form a long line holding hands and a skater at one end of the line stops. The other skaters swing in a circle. What happens to the momentum?

The linear momentum is conserved, but the angular momentum is not. The angular momentum is conserved, but the linear momentum is not. Both angular and linear momentum are conserved. Neither angular momentum nor linear momentum is conserved.

When a spinning figure skater pulls her arms in, she spins faster. Which law best explains the change in speed?

Newton's 1st law Newton's 2nd law Newton's 3nd law Conservation of Angular Momentum Conservation of Energy

A piece of wood is burned in a fireplace. Which of the following is true about the situation?

Mass is conserved. Total energy is conserved. Electric charge is conserved. All of the above are conserved. None of the above are conserved.

A stick of dynamite explodes. How does the momentum of the dynamite before the explosion compare to the total momentum of all of the pieces immediately after the explosion?

The momentum is the same just before and just after the dynamite explodes. The momentum is larger after the explosion. The momentum is larger before the explosion.

When the dynamite explodes, what happens to its mass?

A measurable amount of the mass is destroyed in the explosion. The mass increases as a result of the explosion. All of the mass is still there, but some of the atoms have recombined into different molecules and dissipated through the air.

A medium sized star is rotating about its axis (similar to how the earth rotates about its axis once each day). At the end of its life, it collapses into something called a neutron star which has a much smaller radius than the original star. In the process, there are not forces which would, of themselves, speed up or slow down the rotation of the star. Considering conservation of angular momentum, we would expect the rotation speed of the star to

increase. decrease stay the same it increase or decrease depending on the mass of the star

In a certain nuclear reaction, a radioactive nucleus with a net charge of +6 decays, emits an electron (-1 charge) and a neutrino (no charge), and turns into a nucleus that has a net charge of which of the following choices? (Hint: think about Conservation of Charge. Drawing a picture may help.)

-1 +1 +5 +6 +7

If a quantity is conserved,

the amount and form of that quantity do not change the amount of that quantity can change but not the form the form of the quantity can change but not the amount both the amount and form of that quantity can change

A free neutron (no charge) can decay into a proton (charge of +1), a neutrino (no charge), and one other particle. What does the charge of of the other particle need to be? (***Note: The formula for the reaction has one side with a neutron and the other side has three particles a proton (+1 charge), a neutrino (0 charge), and the mystery particle (? charge).)

-2 -1 0 +1 +2

A cue ball is fired at a group of pool balls on a frictionless pool table. Compare the total momentum before and after the cue ball hits the other balls.

It is the same before and after the collision. It was smaller before the collision. It was larger before the collision.

When paper burns, what happens to its mass?

A measureable amount of the mass is destroyed in the burning. The mass increases as a result of the burning. All of the mass is still there, but some of the atoms have recombined into different molecules and dissipated through the air.

Free Response

What does it mean for a quantity to be conserved?
Name the six conservation principles discussed in this chapter.
What are the two classes of fundamental particles?
If you weigh all of the ingredients before making a cake, and then you weigh the finished cake, what will you find? What accounts for the missing weight?
You are spinning in a swivel chair with your arms and legs straight out. What happens if you pull your limbs in toward you? What conservation principle explains this?
You scuff across nylon carpet while wearing tennis shoes.
- What happens to the electrons in the carpet?
- Does the carpet become positively or negatively charged? How about you and your shoes?
- What has happened to the total charge of the system? What has happened to the total number of electrons? What has happened to the sum of the protons and the neutrons of the system?
- What three conservation principles account for this?
Your friend is trying to learn to ride a unicycle without much success. Your friend first wants to learn to balance while the cycle is stationary before attempting to pedal. Using conservation of angular momentum, explain why your friend may be having difficulties.
In terms of the Carbon Cycle, explain why a growing plant doesn't violate conservation of mass. What conservation principle accounts for this?
Explain how it is possible for police to determine the speed and direction of two vehicles before a crash by measuring the skid marks. What conservation principle allows them to do this?
Explain how pool sharks take advantage of conservation of momentum to improve their game.
Explain how the speed of light being a constant for everyone leads to the conclusion that mass increases with speed.