physics final
Two billiard balls of the same mass roll straight toward each other. The first has a velocity of +5 m/s and the second has a velocity of -3 m/s. After colliding, the first ball has a velocity of
-3 m/s
Two 1 kg billiard balls roll toward each other, each moving with speed 10 m/s. What is the combined momentum of the two balls?
0 kg m/s
An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration is
0 m/s^2
An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration is
0 m/s^2.
A falling skydiver of mass 100 kg experiences 800 N air resistance. The acceleration of the skydiver is
0.2 g
A 1-kg glider and a 3-kg glider both slide toward each other at 2 m/s on an air track. They collide and stick. The combined mass moves at
1 m/s
Doing twice the usual work on an object in four times the usual time requires
1/2 the usual power
If a carʹs velocity changes from 50 km/h to 10 km/h in 4 seconds, its acceleration is
10 km/h/s
A push on a 1-kg brick accelerates it. Neglecting friction, equally accelerating a 10 -kg brick requires
10 times as much force.
The mass of a lamb that weights 110 N is about
11 kg
How much pushing force is needed to accelerate a 50 kg desk at 1 m/ s^2 across the floor if the friction force is 70 N?
120 N
How much pushing force is needed to accelerate a 50 kg desk at 1 m/s^2 across the floor if the friction force is 70 N?
120 N
A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it were traveling at 150 km/hr?
180 m
Disregarding air drag, how fast must you toss a ball straight up in order for it to take 6 seconds to return to the level from which you tossed it?
30 m/s
A 2000-kg car experiences a braking force of 10,000 N and skids to a stop in 6 seconds. The speed of the car just before the brakes were applied was
30 m/s.
A car travels 20 mi/hr for 30 minutes, then travels 40 mi/hr for 30 minutes. What is the average speed for the entire trip?
30 mi/hr
If you need to tighten a bolt with 80 Nm of torque using a wrench with a handle that is 25 cm from the axis of the bolt, how much force do you need to apply when turning the wrench?
320 N
A jack system will increase the potential energy of a heavy load by 400 J and generate 600 J of heat with a work input of 1000 J. The efficiency of the jack system is
40%
A piece of rope is pulled by two people in a tug -of-war. Each pulls with 400 N of force. What is the tension in the rope?
400 N
To do 10 J of work pushing a crate using 2 N of force, you will need to push the crate
5 m
How long will it take to stop a 1500 kg car moving at 20 m/s with a braking force of 6000 N?
5 s
A 10-kilogram block with an initial velocity of 10 m/s slides 10 meters across a horizontal surface and comes to rest. It takes the block 2 seconds to stop. The amount of stopping force acting on the block is about
50 N
You run 12 miles at 12 mi/hr, but then you get tired and walk 12 miles back at 4 mi/hr. What is your average speed for the entire trip?
6 mi/hr
A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?
80 J
A ball starting from rest at the top of an inclined plane accelerates at 2 m/s^2 and reaches the bottom of the plane in 3 seconds. What is the length of the plane?
9 m
A worker with a mass of 100 kg stands on a 50 kg platform suspended at rest by two ropes. The tension in the first rope is measured to be 600 N. What is the tension in the second rope?
900 N
A longer cannon barrel is advantageous because it increases
A and C.
How can you increase the angular momentum of a ball spinning on a string?
A) and B)
Acrobat Bart at the circus drops vertically onto the end of a see -saw, with his partner Art equidistant from the fulcrum at the other end. Art is propelled straight upward a distance twice that of Bartʹs dropping distance. Neglecting inefficiencies we see
Art has half the mass of Bart.
The first scientist to be credited for postulating that Earth circled the Sun was
Copernicus
The first scientist to be credited for postulating that Earth circled the Sun was
Copernicus.
A ball is tossed vertically upward. At its highest point,
a and b
A ring, a disk, and a solid sphere begin rolling down a hill together. The one to reach the bottom last is the
a ring
When a book weighing 3 N is lying at rest on a table, the force that the table exerts on the book is
a support force of 3 N.
It takes 4 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
about 80 m
The famous Leaning Tower of Pisa doesnʹt topple over because its center of gravity is
above a place of support
An example of an object in mechanical equilibrium is an object
all of the above
In class, I laid on a bed of nails with cinder blocks stacked on top of me. When Thomas struck the blocks with the sledgehammer, the kinetic energy of the hammer went into
all of the above
Which of the following statements reflect Aristotleʹs views of motion?
all of these
A simple lever, properly arranged, is capable of multiplying work input.
always false
If you toss a coin straight upward while in a train moving at constant velocity, the coin will land
as if you were at rest.
Concerning a road trip, the biggest concern while figuring drive time is ______________, while driving through a speed trap is ______________, while merging onto an expressway is ______________, and while driving along a one-way street is ______________.
average speed; instantaneous speed; acceleration; velocity
If no external forces are acting on a moving object it will
continue moving at the same velocity
When an object falls through the air, its velocity increases and its acceleration
decreases
A car travels in a circle with constant speed. The net force on the car is
directed towards the center of the curve
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to
follow a straight-line path.
An object is propelled along a straight-line path by a force. If the net force were halved and the objectʹs mass is doubled, the objectʹs acceleration would be
half as much.
When a car is braked to a stop, its kinetic energy is transformed to
heat
Two objects of the same size, but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the
heavier object
An upright broom is easier to balance when the heavier end is
highest, farthest from your hand
An upright broom is easier to balance when the heavier end is
highest, farthest from your hand.
If you toss a coin straight upward in train that gains speed while the coin is in the air, the coin will land
in back of you.
When a twirling ice skater brings her arms inward, her rotational inertia
increases
For every action force, there must be a reaction force that
is equal in magnitude.
A single brick falls with acceleration g. The reason a double brick falls with the same acceleration is
its ratio of force to mass is the same.
A force is a vector quantity because it has both
magnitude and direction
A heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the light truck will have less
momentum
A heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the heavy truck will have greater
momentum.
In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the
moon
A falling skydiver of mass 100 kg experiences 500 N air resistance. The acceleration of the skydiver is
more than 0.5 g
A horse exerts 500 N of force on a heavy wagon. The wagon pulls back on the horse with an equal force. The wagon still accelerates because
nevertheless there is still an unbalanced force on the wagon
A horse exerts 500 N of force on a heavy wagon. The wagon pulls back on the horse with an equal force. The wagon still accelerates because
nevertheless there is still an unbalanced force on the wagon.
If one object has three times as much weight as another object, it also must have three times as much
none of the above
A large heavy truck and a small baby carriage roll down a hill. Neglecting friction, at the bottom of the hill, the baby carriage will have a greater
none of these
In class, we usually have a tug-of-war between 10 women and 10 men. The men compete in their socks while the women keep their shoes on. The women are often able to pull the men to their side. This happens because the women
push harder on the floor than the men do.
When a twirling ice skater brings her arms inward, her angular momentum
remains the same
Your pet hamster sits on a spinning record player. If the angular speed of the record player doubles and he moves to a point twice as far from the center, then his linear speed (assuming he doesnʹt fly off the record player and onto the floor, causing PETA and SPCA to come after you)
remains the same
According to Galileo, the natural tendency of an object is to
resist a change in motion (inertia)
According to Galileo, the natural tendency of an object is to
resist a change in motion.
Centrifugal forces are an apparent reality to observers in a reference frame that is
rotating
Due to the effects of inertia, most people are _____________ in the evening than they are in the morning.
shorter
Due to the effects of inertia, most people are ______________ in the evening than they are in the morning.
shorter
If a crate is pushed across the floor with a force of 50 N and it slowly speeds up, how much is the friction acting on the crate?
slightly less than 50 N
If a crate is pushed across the floor with a force of 50 N and it slowly speeds up, how much is the friction acting on the crate?
slightly less than 50 N.
Which requires the most amount of work by the brakes of a car?
slowing down from 100 km/h to 70 km/h
When braking a car in an emergency, one does not want to jam the brakes and make the tires lock because
static friction is greater than sliding friction
The center of mass of a human body is located at a point
that changes as a person bends over
Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr?
the 60 km/hr car
Which jar will roll down an incline in the shortest time, an empty one or one filled with peanut butter?
the filled jar
A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because
the mass of the rocket decreases as fuel is burned
A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because
the mass of the rocket decreases as fuel is burned.
Which of the following descriptions of an objectʹs state is not equivalent to the others?
the object is at rest
A single brick falls with acceleration g. The reason a double brick falls with the same acceleration is
the ratio of force to mass is the same
A car traveling at 100 km/h strikes an unfortunate bug and splatters it. The force of impact is
the same for both.
Harry pulls on the end of a spring attached to a wall. The reaction to Harryʹs pull on the spring is
the spring pulling on Harry
When trying to turn a stubborn screw, you can generate twice as much torque by switching to a screwdriver with a handle that is
twice as wide.
A skydiver falls towards a lake on the Earth. The attraction of the Earth on the diver pulls the diver down. What is the reaction to this force?
weight of the diver that will soon push down on the water