Physics study

A 12,000 W crane motor can lift a block to a height of 52 meters in a period of 15 seconds. What is the mass of the block? a. 346 kg b. 3462 kg c. 10 kg d. 4160 kg e. 3.4 kg

a

A car starts from rest and accelerates to 30 mph. Later, it gets on a highway and accelerates to 60 mph. Which takes more energy, the 0 to 30 mph, or the 30 to 60 mph? a. 30 to 60 b. 0 to 30 c. both the same

a

A golfer drives her golf ball from the tee down the fairway in a high arcing shot. When the ball is at the highest point of its flight: a. the x-velocity is non-zero and the y-velocity is zero b. the velocity is non-zero and the acceleration is zero c. the velocity and acceleration are both zero d. the x-velocity is zero and the y-velocity is zero

a

Is it possible for an object moving with a constant speed to accelerate? a. Yes, although the speed is constant, the direction of the velocity can be changing. b. Yes, if an object is moving it can experience acceleration c. No, if the speed is constant then the acceleration is equal to zero. d. No, an object can accelerate only if there is a net force acting on it.

a

Who was the first person to realize that the planets move in elliptical paths around the Sun? a. Kepler b. Newton c. Einstein d. Galileo

a

You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will: a. remain vertically under the plane while falling b. not fall at all c. move ahead of the plane while falling d. quickly lag behind the plane while falling

a

A block rests at the edge of a platform that is 10 meters above level ground. Air resistance is negligible. The time it will take for the block to reach the ground is most nearly

a. 1.4 s

A hypothetical planet has a mass of half that of the Earth and a radius of twice that of the Earth. What is the acceleration due to gravity on the planet in terms of g, the acceleration due to gravity at the Earth? a. g/4 b. g/2 c. g d. g/8

d

Does the speedometer in a car measure velocity or speed?

speed

You drop a rock off a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their separation?

the separation increases as they fall

In which of the following situations would an object be accelerated? I. It moves in a straight line at constant speed. II. It moves with uniform circular motion. III. It travels as a projectile in a gravitational field with negligible air resistance.

a. II and III only

You throw a ball straight up into the air. After it leaves your hand, at what point in its flight does it have the maximum value of acceleration?

a. its acceleration is constant everywhere

A ball is thrown straight upward with some initial speed. When it reaches the top of its flight (at a height h), a second ball is thrown straight upward with the same initial speed. Where will the balls cross paths?

above height h/2

A 2 kg object moves in a circle of radius 4 m at a constant speed of 3 m/s. A net force of 4.5 N acts on the object. What is the angular momentum of the object with respect to an axis perpendicular to the circle and through it center? a) 13.5 kg*m^2/s^2 b) 24 kg*m^2/s c) 9 N*m/kg d) 12 m^2/s e) 18 N*m/kg

b

A ball falls straight down through the air under the influence of gravity. There is a retarding force F on the ball with magnitude given by F = bv, where v is the speed of the ball and b is a positive constant. The magnitude of the acceleration a of the ball at any time is equal to which of the following? a. g/b b. g-bv/m c. g+bv/m d. bv/m e. g-b

b

A block of mass 3m can move without friction on a horizontal table. This block is attached to another block of mass m by a cord that passes over a frictionless pulley, as shown above. If the masses of the cord and the pulley are negligible, what is the magnitude of the acceleration of the descending block? a. g b. g/4 c. 2g/3 d. g/3 e. Zero

b

A skier goes over a small round hill with radius R. Since she is in circular motion, where has to be a centripetal force. At the top of the hill, what is Fc of the skier equal to? a) Fc= m*g b) Fc= m*g -N c) Fc= T+N-m*g d) Fc= N e) Fc= N+m*g

b

An object is released from rest on a planet that has no atmosphere. The object falls freely for 3.0 meters in the first second. What is the magnitude of the acceleration due to gravity on the planet? a. 1.5 m/s^2 b. 6 m/s^2 c. 3 m/s^2 d. 12 m/s^2 e. 10 m/s^2

b

When two vectors A and B of magnitudes "a" and "b" are added ; the magnitude of resultant vector is: a. not more than square root of a^2 +b^2 b. Not greater than (a+b) c. equal to (a+b) d. equal to (a-b)

b

You put your book on the bus seat next to you. When the bus stops suddenly, the book slides forward off the seat. Why? a. it did not move, but only seemed to b. no net force acted on it c. a net force acted on it d. it remained at rest e. gravity briefly stopped acting on it

b

You drop a rock off a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their velocities?

both increase at the same rate

A ball tied to a string is being whirled around in a circle. What can you say about the work done by tension? a. tension does positive work b. tension does negative work c. tension does no work at all

c

A car initially travels north and then turns to the left along a circular curve. This causes a package on the seat of the car to slide toward the right side of the car. Which of the following is true of the net force on the package while it is sliding? a. There is not enough force directed north to keep the package from sliding. b. There is not enough force tangential to the car's path to keep the package from sliding. c. There is not enough force directed toward the center of the circle to keep the package from sliding. d. The force is directed away from the center of the circle. e. The force is directed north.

c

A river flowing west to east at speed 3 m/min. A man on the south bank of the river, capable of swimming at 6m/min in still water, wants to swim across the river in shortest time. He should swim in a direction: a. 30 degrees east of north b. 60 degrees east of north c. Due north d. 30 degrees west of north

c

A toy car has 9000 J of kinetic energy when its velocity across a horizontal floor is 6 miles per hour. How much kinetic energy would the car have if its velocity is decreased to 2 miles per hour? a. 1000 J b. 81,000 J c. 3000 J d. 27,000 J e. 4500 J

c

Two equal-mass rocks tied to strings are whirled in horizontal circles. The radius of circle 2 is twice that of circle 1. If the period of motion is the same for both rocks, what is the tension in cord 2 compared to cord 1? T is tension 2 t is tension 1 a) T=1/2*t b) T=t c) T=2*t d) T=1/4*t e) T=4t

c

When an object is released from rest and falls in the absence of friction, which of the following is true concerning its motion? a. its velocity is constant b. neither its acceleration nor its velocity is constant c. its acceleration is constant d. both its acceleration and its velocity are constant

c

Does the centripetal force acting on an object do work on the object? a. Yes, since it takes energy to turn an object. b. Yes, since a force acts and the object moves, and work is force times distance. c. No, because the object has constant speed. d. No, because the force and the displacement of the object are perpendicular.

d

If a car traveling 60 km/hr can brake to a stop within 20 m, what is its stopping distance if it is traveling 120 km/hr? Assume that the braking force is the same in both cases. a. 40 m b. 60 m c. 20 m d. 80 m e. 30 m

d

If you push twice as hard against a stationary brick wall, the amount of work you do a. doubles. b. is cut in half. c. remains constant but non-zero. d. remains constant at zero.

d

Two tug-of-war opponents each pull with a force of 100 N on opposite ends of a rope. What is the tension in the rope? a. 50 N b. 200 N c. 150 N d. 100 N e. 0 N

d

You see a leaf falling to the ground with constant speed. When you first notice it, the leaf has initial total energy Ui + Ki. You watch the leaf until just before it hits the ground, at which point it has final total energy Uf + Kf. How do these total energies compare? a. impossible to tell from the information provided b. Ui+Ki=Uf+Kf c. Ui+Ki<Uf+Kf d. Ui+Ki>Uf+Kf

d

An object is released from rest on a planet that has no atmosphere. The object falls freely for 3.0 meters in the first second. What is the magnitude of the acceleration due to gravity on the planet?

d. 6.0 m/s2

Given that A + B = C, and that lAl + lBl = lCl, how are vectors A and B oriented with respect to each other? a. they are perpendicular to each other b. they are at 45° to each other c. they can be at any angle to each other d. they are parallel but in the opposite direction e. they are parallel and in the same direction

e

The Moon does not crash into Earth because: a. it's in Earth's gravitational field b. the net force on it is zero c. it is beyond the main pull of Earth's gravity d. it's being pulled by the Sun as well as by Earth e. none of the above

e

A ball falls straight down through the air under the influence of gravity. The magnitude of the acceleration a of the ball at any time is equal to 9.8m/s2 that means (assuming down is positive):

e. the velocity of the body increases by 9.8 m/s during each second

When throwing a ball straight up, which of the following is true about its velocity v and its acceleration a at the highest point in its path?

e. v = 0, but a not 0

If the average velocity is non-zero over some time interval, does this mean that the instantaneous velocity is never zero during the same interval?

no