Physics Exam 1
Two identical freight cars roll without friction towards each other on a level track. One car rolls at 2 m/s and the other car rolls at 1 m/s. After the cars collide, they couple and roll together with a speed of
.5 m/s
A hockey puck slides across a frozen pond. If ice friction and air resistance are neglected, the force needed to keep the puck sliding at constant velocity is
0 N
Two billiard balls having the same mass roll toward each other at the same speed. What is the net momentum of the two-ball system?
0 kg*m/s
A rock is thrown vertically upward. At the top of its straight-line path, its velocity is
0 m/s
A 1-kg chunk of putty moving at 1 m/s collides and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty move with a momentum of
1 kg*m/s
A rifle of mass 2 kg is horizontally suspended by a pair of strings so that recoil can be measured. The rifle fires a bullet of mass 1/100 kg at a speed of 200 m/s. The recoil velocity of the rifle is about
1 m/s
A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both move with a combined momentum of
1 unit
A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the larger fish after lunch is
1/6 m/s
A push on a 1-kg brick accelerates the brick. Neglecting friction, to equally accelerate a 10-kg brick requires the force to be
10 times as much
A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is
10 times as much as the force on the 1-kg book
A 10-N block and a 1-N block lie on a horizontal frictionless table. To push them with equal acceleration, we would have to push with
10 times as much force on the heavier block
A ball is moving at 4 m/s and has a momentum of 48 kg•m/s. What is the ball's mass?
12 kg
A commercial jet has a mass of 5,000 kg and the thrust of its engine is 10,000 N. The acceleration of the jet when taking off is
2 m/s^2
A 1000-kg car moving at 10 m/s that brakes to a stop in 5 s has an average braking force of
2000 N
A car has a mass of 1000 kg and accelerates at 2 m/s2. What is the magnitude of the force exerted on the car?
2000 N
A 4-kg ball has a momentum of 12 kg•m/s. What is the ball's speed?
3 m/s
A girl pulls on a 10-kg wagon with a constant force of 30 N. What is the wagon's acceleration?
3.0 m/s^2
Two people, one twice as massive as the other, attempt a tug-of-war with 12 m of rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
4 m
Both ends of a piece of rope are pulled by two people in a tug-of-war. If each pulls with a 400-N force, the tension in the rope is
400 N
A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is
5/6 m/s
A skydiver who weighs 500 N reaches terminal velocity at 90 km/h. The air resistance on the skydiver is
500 N
A block is dragged at constant velocity across a level surface by a force of 6 N. What is the force of friction between the block and the surface?
6 N
A 5000-kg freight car crashes into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg freight car?
6 m/s
A boxer punches a sheet of paper in midair from rest to a speed of 40 m/s in 0.05 s. If the mass of the paper is 0.01 kg, the force of the punch on the paper is
8.0 N
The impulse-momentum relationship is a direct result of
Newton's second law
The conservation of momentum is closely related to
Newton's third law
Which of the following has the largest momentum relative to Earth?
a pickup truck speeding along a highway
Action and reaction forces comprise the parts of
a single interaction
When you step off a bus moving at 10 m/s, your horizontal speed when you meet the ground is
about 10 m/s
When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, the contact time is about 10 times more than for a stiff-legged landing and the average force your body experiences is reduced by
about 10 times
If the mass of an object does not change, a constant net force on the object produces constant
acceleration
Newton's second law directly involves
acceleration
Earth moves about 30 km/s relative to the Sun. When you jump upward in front of a wall, the wall doesn't slam into you at 30 km/s because the wall
and you move at the same horizontal speed, before, during, and after your jump.
An archer shoots an arrow. If the action force is the bowstring on the arrow, the reaction is the
arrow's push on the bowstring
A heavy object and a light object in a vacuum are dropped at the same time from rest. The heavier object reaches the ground
at the same time as the lighter object
A player hits a ball with a bat. If one part of the interaction is the bat against the ball, the other part is the
ball against the bat
Earth pulls on the Moon. Similarly the Moon pulls on Earth, evidence that
both
You're driving down the highway and a lovebug spatters onto your windshield. Which undergoes the greater change in momentum?
both the same
You're driving down the highway and a lovebug spatters onto your windshield. Which undergoes the greater force of impact?
both the same
You're driving down the highway and a lovebug spatters onto your windshield. Which undergoes the greater impulse?
both the same
It is correct to say that impulse is equal to
change in momentum
If an object falls with constant acceleration, the velocity of the object must
continually change by the same amount each second
Suppose you're coasting in a car at 60 km/h and apply the brakes until you slow to 40 km/h. When you suddenly release the brake, the car tends to
continue moving at 40 km/h in the absence of forces
A skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration
decreases
When an object falls through the air and gains velocity, the net force actually
decreases
When bullets are fired from an airplane in the forward direction of motion, the momentum of the airplane
decreases
A ball tossed vertically upward reaches its highest point and then falls back to its starting point. During this up-and-down motion the acceleration of the ball is always
directed downward
A given net force propels an object along a straight-line path. If the net force were doubled, its acceleration would
double
A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is
doubled
When you toss a coin straight up, it moves upward, turns around, and drops. During this time the acceleration of the coin is
downward and constant
An elephant and a feather fall from a tree through the air to the ground below. The force of air resistance is greater on the
elephant
A space probe in remote outer space continues moving
even though no force acts on it
Inside the interior of a truck that moves at constant velocity is a package that drops from the midpoint of the ceiling. The package hits the floor
exactly below the midpoint of the ceiling
The force that accelerates a rocket in outer space is exerted on the rocket by the
exhaust gases
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the rock tends to 1.follow a straight-line path. 2.spiral inward. 3.continue in a circular path. 4.fall straight downward.
follow a straight line path
A player catches a ball. Consider the action force to the ball against the player's glove. The reaction is the
force of the glove on the ball
You use a straw for a pea shooter. The speed of the pea emerging from the straw when you blow through it will be greater if the straw is
full length
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force to stop the car, the force needed to stop the truck is
greater
A car traveling along the highway needs a certain amount of braking force to stop. More braking force is required when the car
has more momentum but must stop in the same distance. has more mass but has the same speed and must stop in the same distance. has the same momentum but must stop in a shorter distance. ***all of the above
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
A ball rests in the middle of a cart. When you quickly jerk the cart forward, the ball
hits the back of the cart
The speed of a bullet fired from a gun will be about the same as the speed of the recoiling gun
if the masses of the bullet and gun are equal
A cannonball fired from a long-barrel cannon will have a greater muzzle velocity because the cannonball receives a greater
impulse
A karate expert executes a swift blow and severs a brick with her bare hand. Equal magnitudes occur for the
impulse on both the brick and the expert's hand. force on both the brick and the expert's hand. time of contact on both the block and the expert's hand. ***all of the above
A heavy block at rest is suspended by a vertical rope. When the block is accelerated upward by the rope, the rope tension
increases
If an object's mass decreases while a constant force acts on it, the acceleration
increases
If you are carrying a heavy bag of groceries and bang your hand against the wall, the concept that best explains why you are hurt is
inertia
You toss a ball upward where air resistance is negligible. After the ball leaves your hand the force on it
is the single force due to gravity, always directed downward
According to the impulsemomentum equation Ft = change in mv, a bungee jumper in fall has momentum which is reduced by the force F exerted by the bungee cord. If m is the mass of the jumper, then v in the equation is the speed of the
jumper
A pair of tennis balls fall through the air from a tall building. One ball is regular and the other is filled with lead pellets. The ball to reach the ground first is the
lead filled ball
A ball is thrown vertically upward. Because of air resistance, its speed when returning to its starting level compared with its initial speed is
less
When you are in the way of a fast-moving object and can't get escape, you will suffer a smaller force if the collision time is
long
Compared with falling on a wooden floor, a wine glass may not break when it falls on a carpeted floor because of
longer time to stop
When a cannon fires a cannonball at a given speed, the smaller recoil speed of the cannon is due to different
masses
A Mack truck and a Mini Cooper traveling at the same speed collide head-on. The vehicle to undergo the greatest change in velocity will be the
mini cooper
A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill the heavy truck has greater
momentum
A falling object that has reached its terminal speed continues to gain
neither
A sandbag is motionless in outer space. A second sandbag with 3 times the mass moving at 12 m/s collides with it and they both stick together and move at a speed of
none of the above
How many forces act on an upwardly tossed coin when it gets to the top of its path?
one- gravity
As a ball falls, the action force is the pull of Earth's mass on the ball. The reaction force is the
pull of the ball's mass on Earth
Suppose a gun were made of strong lightweight material with a pellet that is more massive than the gun. Then firing speed is greater for the
recoiling gun
After a ball tossed upward leaves your hand, the force of gravity on it
remains constant
The force exerted on the tires of a car to directly accelerate it along a road is exerted by the
road
A Mack truck and a Mini Cooper traveling at the same speed collide head-on. The collision force is greatest on the
same
Arnold Strongman and Suzie Small each pull on opposite ends of a rope in a tug-of-war. The greatest force on the rope is exerted by
same
A car traveling at 100 km/h strikes an unfortunate bug that splatters on the windshield. The force of impact is greater on the
same for both
From the same height you simultaneously drop a lightweight tennis ball and a heavyweight bowling ball. When they hit the floor they have the same
speed
The air resistance of falling is greatly affected by an object's frontal area and
speed
A sheet of paper can be pulled from beneath a box of cereal without toppling it if the paper is jerked quickly. This best demonstrates that
the box has inertia
A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to a state of zero acceleration first?
the light woman
A force of 1 N accelerates a 1-kg mass at 1 m/s2. The acceleration of a 2-kg mass acted upon by a force of 2 N is
the same
Consider driving into a massive concrete wall with no "give," versus having a head-on collision at the same speed with an identical car moving toward you at the same speed. It would be more damaging to hit the
the same
A roller coaster car at an amusement park carrying 1 passenger takes 3 min to make its ride from start to finish. Neglecting friction, a car with 5 passengers would take
the same time
The force of a falling apple hitting the ground depends upon
the time of contact with the ground. the speed of the apple just before it hits. whether or not the apple bounces. ***all of the above
In order to catch a fast-moving softball with your bare hand, you extend your hand forward just before the catch and then let the ball ride backward with your hand. Doing this reduces the catching force because the
time of catch is increased
The distinction between impulse and force involves the
time the force acts
Recoil is noticeable if we throw a heavy ball while standing on a skateboard. If instead we go through the throwing motion but hold onto the ball, without friction effects our net recoil will be
zero
The force required to maintain an object at a constant velocity in free space is equal to
zero
The net force on any object moving at constant velocity is
zero
When a falling object has reached its terminal velocity, its acceleration is
zero