midterm 2

Question 1

If there was a closed hydraulic system, and one side had a surface area of 100 in2 and the other side had a surface area of 10 in2. What would be the output force on the large end (100 in2) if the small end (10 in2) was pushed with a force of 10 pounds?

Answer 1

100 pounds

Question 2

If there were two balls completely submerged in water called ball Q and ball P. If the balls had the same mass, and ball Q had a volume larger than ball P, what do you know about the gravitational and buoyant forces?

Answer 2

The gravitational force is the same for both balls and the buoyant force is greater for ball Q than ball P.

Question 3

Pressure only depends on the surface area of the fluid and does not depend on the depth.

Answer 3

False

Question 4

Where would you expect the air pressure due to our atmosphere to be largest here on Earth?

Answer 4

sea level

Question 5

If you had three fluids A, B, and C. One way to determine the relative densities of fluids A, B, and C is to mix them together. Over time the most dense fluid will rise to the top, and the least dense fluid will sink to the bottom.

Answer 5

false

Question 6

Special Relativity only works when all objects are not accelerating.

Answer 6

true

Question 7

According to special relativity no information can go faster than the speed of light. That means if the Sun disappeared the people on Earth would not know it was gone for about 8 min and 20 sec.

Answer 7

true

Question 8

If someone was traveling close to the speed of light in a spaceship and the had a stick that was one meter long pointed in the same direction as the spaceship was traveling. What would an outside observer say about the meter stick?

Answer 8

The stick is shorter than one meter

Question 9

If someone was traveling close to the speed of light in a spaceship and the had a clock that was started and stopped after 10 seconds. While the clock was ticking an outside observer started and stopped at the same time. What would an outside observer say about the measured time?

Answer 9

The outside observer would say the time was greater than 10 sec.

Question 10

What is pressure? How can you determine if something has higher or lower pressure?

Answer 10

total force on an object divided by area over which the force is applied. Pressure = force/area.
increase force-increase pressure. decrease area-increase pressure.

Question 11

How can you calculate the output force for a closed hydraulic system if I tell you the input force, and surface area of both sides?

Answer 11

PressureLeft = PressureRight
ForceL/AreaL = ForceR/AreaR

Question 12

What do we know about the pressure due to the atmosphere here on Earth?

Answer 12

They are unbounded fluids. Pulled to center of earth by gravity. It gets stronger in depth.

Question 13

What if you had two balls with the same masses but different volumes? What would be their gravitational and buoyant force?

Answer 13

gravity pulls down and buoyant force pushes upward. object accelerates in direction of net force (direction of stronger forces).
bigger volume has more buoyant force against it while the smaller has less. equal gravity.

Question 14

What if you had two balls with different masses but the same volume? What would be their gravitational and buoyant force?

Answer 14

bigger mass/weight has more gravity force against it while the other has less. equal buoyant force.

Question 15

What is the definition of density?

Answer 15

density= mass/volume

Question 16

What is the fastest information can travel in the universe?

Answer 16

at the speed of light. 670,000,000mph

Question 17

How does an outside observer measure your time and length when you are going really fast (close to the speed of light?

Answer 17

time is longer, length is shorter

Question 18

If you are not accelerating is there anyway to tell if you are moving?

Answer 18

by using Inertial Frame of Reference. the laws of nature remain the same for all observers in inertial frames of reference. like we stand still but to the earth we move. RELATIVITY.

Question 19

What did the Michelson Morley teach us about light? (I went over this in class for little while. Look in your book or look online for more information)

Answer 19

Light travels at the same speed no matter what direction.

1. Speed of Light same for everyone.
2. The laws of physics are same for everyone (no acceleration). doesn’t follow galilean relativity.

Question 20

How does kinetic energy work?

Answer 20

energy of motion.

KE= 1/2mass * speed^2

Question 21

What is gravitational potential energy?

Answer 21

stored energy in an object that has potential to fall.

GPE = weight * height

Question 22

What is potential energy? How can you increase the potential energy between charges?

Answer 22

stored energy.
moving positives together.
moving opposites away from each other.

Question 23

What is work in physics?

Answer 23

how energy is spent.

work= force * displacement

Question 24

How is kinetic energy and potential energy related for the pendulum?

Answer 24

They are constantly moving for kinetic but their is potential for it to fall cause of gravity.

Question 25

What are convection, conduction, and radiation? Can you think of an example of each of these heat transferring processes?

Answer 25

convection: hot materials moves and transfers its heat to colder material.
- firemen running the buckets back and forth to fire.

conduction: objects having different temperatures are placed in direct contact with each other. no perceptible motion.
- firemen passing buckets from one to another.

radiation: direct transfer of energy from one place to another without any need for intervening matter.
- firemen spraying fire from source.

Question 26

There will be a conservation of momentum problem. I will give you the masses of two cars. One car will hit another car at rest. After the collision the first car stop. Given that you know the starting speed of one car can you calculate the new speed of the car that was hit?

Answer 26

MV(before)=MV(after)

solve for V

Question 27

This is the exact question: If there was a small car with a mass of 1,000kg traveling at a velocity of 20m/s (45mph) that collided with a semi truck at rest 10,000kg. Assuming the small car stopped at impact what is the truck’s speed after impact? (Hint conservation of linear momentum)

Answer 27

2 m/s

Question 28

Conservation of Mass:

Answer 28

Conservation of Mass: mass always the same after physical process.
Ex. Baking cookies. dough same as ingredients. add steam with baked and the same again.

Question 29

Conservation of Charge:

Answer 29

Conservation of Charge: moving charge of electrons.

Ex. rubbing ballon on head. doesn’t create new charge, just redistributes

Question 30

Conservation of Energy:

Answer 30

that energy can be neither created nor destroyed. 1st law of thermodynamics.
ex. dropping a rubber ball and it bouncing back.

Question 31

Conservation of angular momentum:

Answer 31

AM= massvelocity(speed)radius.

ex. top, spinning faster it can balance

Question 32

conservation of linear momentum

Answer 32

LM=Mass*Velocity, measures amount of motion in a straight line.
ex. car wreck, what ways they went and tire skids. Pool, what way the ball will go.