Missed Questions

Question 1

Which of the following is the best description of a velocity?
a. 60 miles per hour b. 30 meters per second c. 30 km at 45 degrees north of east d. 40 km/hr e. 50 km/hr southwest

Answer 1

(E) Because velocity is a vector, it should have both a magnitude and direction

Question 2

A ball falls freely toward the earth. If the action force is the earth pulling down on the ball, the reaction force is:
a. the ball pulling up on the earth b. air resistance acting on the ball c. the ball striking the earth when it lands d. the inertia of the ball e. there is no reaction force in this case

Answer 2

(A) Newton’s third law states that if the earth is pulling on the ball, the ball is pulling on the earth.

Question 3

A 0.5 kg ball is dropped from a third-story window that is 10 m above the sidewalk. What is the speed of the ball just before it strikes the sidewalk?

Answer 3

PE at the top of the building = KE at the bottom.

Question 4

The period of revolution is:

Answer 4

Period is measured ONLY in units of time (seconds, minutes, hours, years) and CANNOT be represented as something such as “2 rev/s”. Frequency NOT period, needs both the time and number of revolutions

Question 5

A ball is tied to a string and swings around a center point. If the ball has velocity v, what will be the new velocity if the radius is shortened to 1/2 of its original length?

Answer 5

Since angular momentum is conserved and is equal to mvR, if R is halved, than v must double.

Question 6

Given a force vs. displacement graph for an ideal spring, what is the work done in stretching the spring from a to b m?

Answer 6

The work is equal to the area under the graph from x = a to x = b

Question 7

A mass on an ideal spring vibrates between points A and E as shown. At which point is the acceleration of the mass the greatest?

Answer 7

With the spring hanging from the ceiling, the acceleration is greatest RIGHT when the mass is released. The acceleration is NOT constant throughout the system because there is a spring force. This force is only applied, however, when the spring is stretched. Therefore, because the spring is slack at its topmost point, there is no spring force and the acceleration is just gravity.

Question 8

If an electron enters a magnetic field directed down the page at an angle parallel to the field, what will be the path of the electron?

Answer 8

It will continue to move down the page in a spiral motion.

Question 9

As a wave passes from a spring to another spring with a greater tension…

Answer 9

the speed of the wave increases

Question 10

Which of the following mirrors converge parallel light rays to a focal point?

Answer 10

concave mirror

Question 11

The conversion between mechanical energy and heat energy was first developed by

Answer 11

Joule

Question 12

A 50 g sample of metal is heated to 100 C and then dropped into a beaker containing 50 g of water at 25 C. If the specific heat capacity of the metal is 0.25 cal/g C, what is the final temperature of the water?

Answer 12

Since heat is transferred and no work is done, the heat lose by the metal must equal the heat gained by the water:
mMetalcMetaldeltaTmetal - mWatercWaterdeltaTwater = 0

Question 13

Electromagnetic spectrum in order from lowest to highest frequency

Answer 13

radio, microwave, infrared, visible, ultraviolet, X-ray, gamma

Question 14

Which of the following graphs best represents the length L of a horizontal meter stick traveling horizontally with speed v as it approaches the speed of light?

Answer 14

the length of a meter stick is CONSTANTLY decreasing as long as the speed is increasing. It is approaching zero as the velocity approaches the speed of light

Question 15

A pilot of a spaceship traveling at 90% the speed of light (0.9 c) turns on its laser headlights just as it passes a stationary observer. What will the pilot and observer, respectively, witness the speed of the light coming out of the headlights to be?

Answer 15

both will witness it to be c. This is in corespondance with the second postulate of special relativity that states that “the speed of light is constant in all reference frames, regardless of any relative motion between an observer and the light source.”

Question 16

A Jar remains at rest on a table when a piece of paper is pulled out from under it. Why?

Answer 16

the jar’s inertia causes it to stay at rest. Newton’s first law = law of inertia. inertia is the resistance of an object to changing its state of motion or state of rest. SI unit for inertia = kilogram. It is difficult to push a car to get it moving from a state of rest because of its inertia.

Question 17

Two teams pull against each other on a rope that is stretched across a stream. What is the tension in the rope? How to find it?

Answer 17

Newton’s third law. For every action there is an equal and opposite reaction. The force of the team pulling on the rope is equal and opposite to the force the rope pulls on the team (= tension in rope)

Question 18

Review 8 and 9 in practice test 1

Answer 18

Etc.

Question 19

Wave length is measured from crest to crest. Be careful when measuring the length of a string of a standing wave, as the antinodes will confuse you. Don’t accidentally double the real length

Answer 19

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Question 20

A ball of mass m is thrown at a ball with a speed v and bounces off elastically and horizontally. What is the magnitude of the change in momentum of the ball?

Answer 20

2mv. The original momentum was mv but the new one is -mv -> a net change of 2mv.

Question 21

Force vs. time graphs for the force acting on the ball while it is in contact with the wall?

Answer 21

The force starts out small as the ball first makes contact with the wall, then gets larger as the ball is squashed against the wall, then smaller again as it rebounds from the wall.

Question 22

At the equilibrium position for a mass on a string, there is ________ energy.

Answer 22

ONLY kinetic energy. The mass is at its maximum speed and therefore has no potential energy.

Question 23

On a cold morning, a metal floor feels colder to your feet than a wood floor because?

Answer 23

The heat from your feet is more readily conducted to the metal because the metal is a good conductor, leaving your feet with a lack of heat and feeling cold.

Question 24

All waves can be _______

Answer 24

refracted.

Question 25

Only ______ waves can be polarized, that is, made to vibrate in only one plane.

Answer 25

Mechanical. Sound is a longitudinal wave and therefore cannot be polarized.

Question 26

Which scientist suggested that light could be thought of as packets of energy and that the exact quantity of energy could be determined by the equation E = hf?

Answer 26

Albert Einstein’s photoelectric effect

Question 27

Which scientist determined that the atom consisted mostly of empty space with a small, dense, positive nucleus?

Answer 27

Ernest Rutherford (RUTHLESS -> got lots of GOLD) (element that he shot nuclei at)

Question 28

This law describes the direction an induced current must flow so that the induced magnetic field opposes the change in flux of the original magnetic field.

Answer 28

Lenz’s law

Question 29

How to find APPARENT weight inn an accelerating elevator

Answer 29

apparent weight - normal force… ma = Fn - Fg

Question 30

During one complete cycle, a wave moves through:

Answer 30

1 wavelength, 1 period, and 4 amplitudes

Question 31

Monochromatic light passes through two narrow slits and is projected onto a screen creating a double-slit interference pattern. Which of the following is true? (4 ARE all true)

Answer 31

1. the double-slit interference pattern is evidence that light has a wave characteristic 2. The path difference to the first maximum is equal to the wavelength 3. Increasing the separation between the two slits will compress the observed interference pattern 4. Increasing the wavelength will cause the maximums displayed on the screen to spread out

Question 32

Concave lenses (give symbol) can create only

Answer 32

)( virtual, upright, near side of the lens

Question 33

Converging lenses (give symbol) can create

Answer 33

() both virtual AND real images. same side = virtual and opposite side = real (if outside f) or virtual (if inside f)

Question 34

Converging mirror (concave) (give symbol)

Answer 34

) inside f = virtual, far side outside f = real, same side

Question 35

Diverging mirror (Convex) (give symbol)

Answer 35

( always forms a small, upright, virtual image (far side)

Question 36

The direction of an electric field is

Answer 36

the same as the direction of force acting on a positive charge.

Question 37

Electric potential (voltage) equation

Answer 37

V = kq/r (sigma when there are multiple charges)

Question 38

emf equation

Answer 38

emf = BLv

Question 39

A sound wave emitted by a source has a frequency f, a velocity v, and a wavelength lambda. If the frequency is doubled, how will the speed and wavelength be affected?

Answer 39

velocity only changes when changing mediums. therefore v is constant and lambda = 0.5*lambda

Question 40

Harmonics equation

Answer 40

lambdaN = 1/n * lambda1 where n is the number assigned to the harmonic

Question 41

How to decrease the distance between bright bands in Young’s double-slit experiment:

Answer 41

Recall that Xm = mlambdaL/d, where Xm is the distance between bright bands on the screen. To decrease Xm, decrease lambda (wavelength), L (distance from screen to slits), increase d (distance between slits)

Question 42

Isothermal process

Answer 42

temp remains constant and change in internal energy is 0.

Question 43

Isometric process

Answer 43

volume remains constant and therefore no work is done.

Question 44

Always remember to convert between C and K

Answer 44

Always remember to convert between C and K