Physics Review

A uniform electric field has a magnitude of 10 N/C and is directed upward. A charge brought into the field experiences a force of 2 N upward. The charge must be

+.2 C

Two current carrying wires are parallel to one another and separated by 1 cm. If the distance b/w them is increased to 2 cm the new force will be what factor times the original force?

1/2

A defensive lineman picks up a fumbled football and heads toward the end zone. His mass is 150 kg and velocity is 6 m/s west. A wide reciever with a mass of 90 kg tries to stop the lineman with a head on collision. How fast does the receiver be running if he wants to stop the lineman?

10 m/s (150x6) = (90x10)

An 80 kg football player travels to the right at 8 m/s and a 120 kg player on the opposite team travels to the left at 4.0 m/s. the total momentum is

160 kg m/s to the right (80x 8)-(120x4)= 160 kg

A child runs at 3.0 m/s and jumps onto a sled, initially at rest. If the child's mass is 36 kg, and if the child and sled slide off together at 2.0 m/s after the collision, the sled's mass is

18 kg

Suppose you throw a ball vertically downward with a speed of 10 m/s. What's the speed of the ball 1 second later?

19.8 m/s

A box is moved 20 m across a smooth floor by a force making a downward angle with the floor, such that there is effectively a 10 N force acting parallel with the floor and a 5 N force perpendicular with the floor. The work done is

200 J (20 x 10 N= 200 J)

A capacitor consisting of two parallel plates separated by 2 cm has a potential of 40 V on the top plate and 0 V on the bottom plate. The electric field in the middle is

2000 N/C downward

A painter with a mass of 70 kg climbs a 3.0 m ladder. The painte's PE has increased by

2058 J (70x3.0x9.8= 2058 J)

A crate is acted upon by a force of 100 N. An acceleration of 4 m/s^2 results. The WEIGHT of the crate is

245 N

A man weighs 650 N while on Earth. If he's transported to Mythos, which has same mass as earth but 5x larger, his weight would be:

26 N

a pendulum swings through 10 cycles in 2 seconds. The frequency of the pendulum is

5 Hz (swings/time)

An auto moves 10 m in the first second of travel, 15 in the next, and 20 in the third. What's the acceleration

5 m/s^2

In order to go from rest to 50 m/s^2 in 10 s, a jet must be able to accelerate at

5 m/s^2

A transformer is to be used to step down voltage form an alternating current source from 220 V to 110 V. If the primary has 120 turns, then the number of turns in the secondary is

60

If two metal balls have a charge of -10^-6 and the repulsive force b/w them is 1 N how far apart are they?

9.5 cm

The magnetic pole near the Earth's north geographic pole actually has to be

A S pole, because it has to attract the N pole of your compass needle

Three equal negative charges are placed at three of the four corners of a square. The direction of the electric field at the remaining corner of the square is

Along the line connecting this corner to the opposite corner, and toward the center.

When you shuffle your feet across carpet on a dry day, you can accumulate charge. The fact that you accumulate charge means that the carpet is

An insulator because if it weren't, the charge would immediately leave you.

Object A moving due east collides with object B moving due west. After the collision, A is moving 20 degrees north of due east. What must be true of B after the collision?

At least part of B's velocity must be toward the south

a 10 uC charge is at the origin. A -15 uC charge is on the x-axis 10 cm to the right of the origin. At what point other than infinity can a 1 uC charge be placed so that there will be no net electrostatic force on it?

At one point of the x axis to the left of the positive charged

A rifle bullet is fired horizontally and at the same time another bullet is dropped from rest at the same height. Which bullet strikes the earth first?

Both strike at the same time

A football is thrown upward. the acceleration vector of the football is

downward

an object rises at 5 m/s under the influence of gravity. 1 second later the object is

falling at 4.8 m/s

Two people sit face to face on skateboards that are free to roll w/o friction. They push each other with a force of 40 N and move apart. Person X whose mass is 50 kg, moves to the left at 3 m/s. Person Z whose mass is 60 kg is

moves to the right at 2.5 m/s

A long straight wire carries a current. A positive charge moves toward the wire in a direction perpendicular to the wire. The direction of the force on the charge will be

parallel to the wire opposite the direction of the current

When a baseball bat hits the ball, the impulse delivered to the ball is increased by

the "follow through" on the swing, which increases contact time

The acceleration of a body cannot be zero at a point where

the instantaneous velocity is positive but decreasing

If a charge of -3 x 10^-6 C were allowed to fall through potential difference of +500 V, the change in PE for the charge would be

-1.5 x 10^-3 J

Two long bar magnets are aligned so the the N poles face each other. The magnets are separated 1 cm apart and a repulsive force b/w the N poles is .04 N. When the separation increases to 2 cm the force will be

.010

A bullet fired horizontally at a target 20 m away. The velocity of the bullet is 200 m/s. How much will the bullet drop on the way to the target?

.05 (idk why tho)

the mass of an apple on earth is .2 kg. On the moon the mass of the same apple would be:

.2 kg

The PE of a spring is .3 J when it is compressed .04 m to the left of its equilibrium position. At this point it comes to its leftmost position. What is its KE when it returns to the equilibrium point?

.3 J and moving to the right

a ball is projected upward with an initial velocity of 10 m/s It will reach its max height in approx

1 second

a cyclist races around a circular track at a constant speed of 20 m/s The radius of the track is 40 m. The centripetal acceleration of the cyclist is:

10 m/s^2

A parachutist jumping from an airplane reaches terminal velocity when the force of air resistance is 980 N. The mass of the parachutist is

100 kg (9.8 x 100)= 980 air resistance

Two equal charges repel one another with a force of 4.0 x 10 -4 N when they are 10 cm apart. (coulomb's constant is k= 9.0 x10^9 N x m^2/C^2). If they are moved until the separation is 5 cm the repulsive force will be

16 x 10^-4 N

An object weighs 30 N on Earth. What is the approximate mass?

3 kg (1 N= .1 kg)

A man standing on a bridge throws a stone horizontally at 20 m/s. The stone hits the water 2.5 s later. The bridge is

30.6 m high

a car is decelerating at a rate of 2 km/s^2. If its initital speed was 66 km/s how long will it take the car to come to a complete stop?

33 s

If the speed of a car is doubled but the brakes apply the same force, the distance to stop the car changes by a factor of

4

An object with a KE of 40 J is stopped at a distance of .01 m. The average force that stops the object is

4,000 N (40/.01 = 4,000)

An iron robot falls from rest. What distance has it fallen in the first 3.5 seconds?

60 m

Your mass is 50 kg. Suppose you're standing on a scale in an elevator rising upward at the rate of 3 m/s every second. What would be the reading on the scale?

640 N

A body travels at an initial speed of 2.5 m/s^2. Given a constant acceleration of .2 m/s^2, what is the speed of the body 25 s later

7.5 m/s (.2 x 25)+ 2.5= 7.5

A quantity that is a measure of how the velocity of a body changes with time is

Acceleration

A tennis ball thrown upward reaches its slowest point at

C) the highest point on the parabola

if a force performs work on an object, the object must have...

Changed its position

The south pole of a bar magnet is moved toward an aluminum ring along the axis of the ring. AS the magnet approaches the changing magnetic flux induces an electric current in the ring that when seen from a bar magnet, corresponds to positive charge carriers flowing

Clockwise

Force F, acting on time T, and over a distance D, gives impulse I. To get the same impulse using half the force, it would be necessary or the force to act

For a time 2T

A box is pushed eastward across a rough horizontal surface by a force acting parallel to the floor. A force providing an impulse directed westward on the body is

Friction

You have a pair of horizontal parallel plates, with the positive plate above the negative plate. How will the lines of constant potential be arranged in this perspective?

Horizontally

A brick slides across a horizontal rough surface and eventually comes to a stop. What happened to the KE of the brick?

It was converted to other energy forms, mostly heat

an object undergoes uniform circular motion. Which pair of vectors is perpendicular?

Its centripetal acceleration and velocity vectors

All except one of the following require application of net force. Which is the exception?

Maintaining an object in motion at a constant velocity

The principle that total momentum does not change during a brief collision is a result of

Newton's second and third law

The electric field created by a moving negative charge

Points toward the charge

A rubber rod is rubbed with fur so that the fur becomes positively charged. The rod is then used to charge an electroscope. The charge on the electroscope will be

Positive IF charged by induction

The starship Enterprise locks onto an alien ship and starts to pull it towards itself. Which ship has greater acceleration?

The Enterprise

When a net horizontal force of 250 N acts on a 50 kg cart that's free to roll on a level surface,

The cart accelerates at 5 m/s^2

A battery causing a large current in a solenoid. A bar magnet is held at rest nearby, aligned with the axis of the solenoid, with its S pole closest to the solenoid. The bar magnet is being repelled by the solenoid. Which of the following statements is true of the conventional current in the solenoid?

The current in the solenoid is flowing clockwise as seen from the bar magnet

Two equal positive charges are near eachother. If we increase the amount of charge on just one of them, then

The electric field at the position of the smaller charge increases

a gun is made of a super-low weight but strong material. The bullet for the gun is more massive than the gun itself. For such a gun

The gun, if unsupported, would have a recoil velocity higher than the bullet velocity

Which has the greatest KE: a 1-ton car moving at 30 m/s or a half ton car moving at 60 m/s?

The half-ton car

Two particles move into a magnetic field. They enter moving at the same speed and direction. The magnitude of the charge on each is known to be the same. One particle curls to the right, and the other to the left upon entering the field, the one on the left moving in a larger circle than the right one. From this we can say that

The leftward moving particle has more mass and its charge is opposite the other particle.

A bar magnet broken in half and the magnetic field around one piece is mapped out. What is wrong with the picture?

There's no south pole.

Which is stronger, the Earth's pull on the moon or the moons pull on Earth?

They're the same

Suppose an artificial satellite is put into orbit around Earth at a distance 1/4 from the center of Earth to the center of the moon. In terms of the moon period Tm, what will the period of the satellite be?

Tm/8

Two astronauts of equal mass are holding on to eachother and moving at a speed of 30 m/s They push off each other and one of the astronauts moves in the same direction as the two were initially moving but at 60 m/s The velocity of the second astronaut is

ZERO

A common experience is to find that a steady pull is required to keep an object moving at a constant velocity, even on a level surface, when friction is present. Analyzing this experience in light of Newton's laws of motion, the conclusion is:

a frictional force exactly opposes your pull and the FIRST law applies

Two identical coils of wire are placed on a single horizontal wooden broom handle. The coils are separated by a few cm. We now run identical currents in the same direction through each coil. The coils experience

an attractive magnetic force

After their rocket engines shut off, astronauts experience weightlessness in the orbiting space shuttle,

and they are accelerating because they are actually in free fall

An object is acted upon by the 3 forces in fig 1. In order to move the object upward:

any upward force can be applied

Imagine that this classroom contains a constant magnetic field that points from the front to the back. In front of you a negative charge is slowly moving horizontally to your left. As you watch, the magnetic force on the charge

deflects the charge into a counterclockwise vertical circle

Suppose a planet has a mass of 10x that of earth and a radius 100x earth's. The acceleration gravity on the surface of the planet is

g/1000

The orbit of Comet UX209 about the sun is 365 days, like earth. It's closer to the sun in April than it is in October. Thus the speed of UX209 as it moves along its orbit is:

greater in april than in october

If the plates of a charged parallel plate capacitor were moved further apart, the PE of each of the charges on the capacitor would

increase.

A bullet is fired straight down from a helicopter. neglecting air resistance, the velocity of the bullet

increases 9.8 m/s each second

The S pole of a bar magnet is moved toward a short helical coil of wire along the axis of the coil. The coil has 100 turns and the end of the coil are connected to form a closed circuit. If the coil is replaced with a single loop of the same wire, and the magnet is moved exactly as before the current induced in the loop is

repulsive and 100 times smaller

A grandfather clock that is regulated by a pendulum is taken to the moon, where the acceleration of gravity is less. Compared to an identical clock on Earth, the grandfather clock on the moon will

run slow

You stand on a scale. The reaction to the force the Earth exerts on you is

the force you exert on the Earth

Two cars that have the same mass are moving around a circular track at the same constant speed. The track is perfectly level. If car 1 is at the inner edge of the track and car 2 is at the outer edge, then

the frictional force on car 1 is grater than that on car 2

you toss a ball straight up in the air. At the highest point the ball's

velocity is zero

a 10 kg sack of potatoes falls from an airplane. As the velocity of the falling sack increases, so does the air resistance on it. When the air resistance equals 98 N, the acceleration of the sack will be:

zero (10 kg x 9.8 m/s) = 98 N