physics test 2 (4,5,6)
An apple weighs 1 N. When the apple is held at rest above your head, the net force on the apple is
0 N.
A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200 N, the sack's acceleration become
0 m/s/s
An apple at rest weighs 1 N. The net force on the apple when it is in free fall is
1 N
A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. Both move with a combined momentum of
1 unit.
Two identical gliders slide toward each other on an air track. One moves at 1 m/s and the other at 2 m/s. They collide, stick, and moves at
1/2 m/s.
A 1-kg mass at the Earth's surface weighs
10 N.
The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is
10 N.
A rock is thrown vertically into the air. At the top of its path, its acceleration is
10 m/s/s
A push on a 1-kg brick accelerates it. Neglecting friction, equally accelerating a 10-kg brick require
10 times as much force.
A river 100 m wide flows due south. A boat that goes 1 m/s relative to the water is pointed due east as it crosses from the west bank. The boat crosses in
100 s.
A bag of groceries that has a mass of 10 kilograms weighs about
1000 N.
A 5000-kg freight car moving at 2 m/s collides with a 10,000-kg freight car at rest. They couple upon collision and move away at
2 m/s
The average braking force of a 1000-kg car moving at 10 m/s braking to a stop in 5 s is
2000 N.
A car traveling at 22 m/s comes to an abrupt halt in 0.1 second when it hits a tree. What is the deceleration of the car?
220 m/s/s
The airspeed of an airplane is 200 km/h. When it is caught in a 200-km/h crosswind, its speed across the ground below is
283 km/h.
The speed of a 4-kg ball with a momentum of 12 kg m/s is
3 m/s.
A 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is then
300 N upward.
A 1000-kg automobile enters a freeway on-ramp at 20 m/s and accelerates uniformly up to 40 m/s in a time of 10 seconds. How far does the automobile travel during that time
300 m
When a karate chop breaks a board with a 3000-N blow, the amount of force that acts on the hand is
3000 N.
A piece of rope is pulled by two people in a tug-of-war. Each exerts a 400-N force. What is the tension in the rope?
400 N.
A vertical vector of 3 units combined with a horizontal vector of 4 units has a resultant of
5 units.
The human body can withstand an acceleration of 10 g under certain conditions. What net force would produce this acceleration for a 50-kg person
5000 N
Two 5000-kg rail cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple, and roll together with a combined momentum of
5000 kg m/s.
A 10-N falling object encounters 4 N of air resistance. The net force on the object is
6 N
If all people, animals, trains and trucks all over the world began to walk or run towards the east (opposite the direction of Earth's spin), then
Earth would spin a bit slower.
The impulse-momentum relationship is a direct result of
Newton's 2nd law.
The conservation of momentum is most closely related to
Newton's 3rd law.
A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle that undergoes the greatest change in velocity will be the
Volkswagen.
It is correct to say that impulse is equal to
a corresponding change in momentum.
Which of the following has the largest momentum relative to Earth's surface?
a pickup truck speeding along a highway
If more horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object
accelerates in the direction of the applied force.
A constant net force on a rail-road car produces constant
acceleration.
If an apple experiences a constant net force, it will have a constant
acceleration.
If several balls are thrown straight up with different initial speeds, the quantity that will have the same value along their paths is their
acceleration.
Your friend says that the heavyweight champion of the world cannot exert a force of 50 N on an isolated piece of tissue paper with his best punch. You
agree that it can't be done, the paper cannot exert 50 N.
As the sloped surface supporting a shoe becomes steeper
all of these.
Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much
all of these.
Which has zero acceleration? An object
all of these.
A red car has a head-on collision with an approaching blue car with the same magnitude of momentum. A green car driving with the same momentum as the other cars collides with an enormously massive wall. Which of the three cars will experience the greatest impulse?
all the same
When a skateboarder pushes on a wall,
all these.
Action and reaction pairs of forces
always act simultaneously.
An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the
arrow's push against the bowstring.
Two vehicles with equal magnitudes of momentum traveling at right angles to each other undergo an inelastic collision. The combined wreck moves in a direction
at 45 degrees to the direction of either car before collision.
Neglecting friction, a small and a large block of ice begin sliding down an incline together. The larger block reaches the bottom
at the same time as the small block.
As a ball falls, the action force is the Earth's pull on the ball. The reaction force is the
ball's pull on Earth.
Which produces more force: driving into a very massive concrete wall with no "give," or having a head-on collision with an identical car moving toward you at the same speed?
both are the same.
Nellie Newton pulls her sled by a rope that is 45° to the horizontal. The horizontal and vertical components of force are
both of these.
When a vertically falling firecracker bursts, the vector sum of momentum fragments
both of these.
You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater change in momentum during the time of contact?
both the same
Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is
both the same.
A karate chop is more effective if one's hand
bounces upon impact.
The greater efficiency achieved with the curved blades of a Pelton wheel is due to
bouncing
A cannon recoils while firing a cannonball. The speed of the cannon's recoil is relatively small because the
cannon has much more mass than the cannonball.
When bullets are fired from an airplane in the forward direction, the momentum of the airplane is
decreased
Which has the greater momentum when moving?
either of these depending on speed
The force that propels a cannonball when fired from a cannon is
equal and opposite to the force the ball exerts on the cannon.
If vertically falling rain makes slanted 45° streaks on the side windows of a moving car, the speed of the car
equals the speed of the falling drops.
When a boxer hits a punching bag, the strength of his punch depends on how much force the bag can
exert on the boxer's fist.
The force that accelerates a rocket in outer space is exerted on the rocket by the
exhaust gases.
When you drop a rubber ball on the floor it bounces back. The force exerted on the ball to produce bouncing is by the
floor.
A player hits a ball with a bat. If action is the force of the bat against the ball, reaction is the
force that the ball exerts on the bat.
The newton is a unit of
force.
A player catches a ball. If action is the force of the ball against the player's glove, reaction is the
glove against the ball.
Two vehicles with equal magnitudes of momentum traveling at right angles to each other undergo an inelastic collision. The magnitude of momentum for the combined wreck is
greater than the magnitude of momentum of either car before collision.
Whether a truck comes to a stop by crashing into a haystack or a brick wall, the stopping force is
greater with the brick wall.
A pair of air pucks on an air table are set in motion when a compressed spring between them is released. If one puck moves with twice the speed of the other, then its mass is
half the mass of the other.
A skydiver's terminal velocity will be greatest if she falls
head first.
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.
Nellie's weight and normal force usually have the same magnitude when she stands on a
horizontal surface.
A softer landing occurs when an falling object bounces from a surface
in a extended time.
When a boxer moves into an oncoming punch, the force experienced is
increased
If an object's mass is decreasing while a constant force is applied to the object, the acceleration
increases.
An object with twice as much mass as another object has twice as much
inertia.
For every action force, there must be a reaction force that
is equal in magnitude
A heavy block at rest is suspended by a vertical rope. When the block accelerates upward by the rope, the rope tension
is greater than its weight.
Whenever the net force on an object is zero, its acceleration
is zero.
Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard encounter
lengthened time of contact.
A pair of toy freight cars, one twice the mass of the other, fly apart when a compressed spring that joins them is released. Acceleration will be greater for the
lighter car.
If you can't avoid being hit by a fast-moving object, you'll suffer a smaller contact force if you can extend that force over a
longer time.
A kilogram is a measure of an object's
mass.
A rock is thrown vertically into the air. At the top of its path the net force on it is
mg.
A same-size iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater
momentum.
When Nellie hangs suspended from a pair of ropes that are not vertical, the tension in each rope is
more than half her weight.
An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will
move in the opposite direction at a lower speed.
A fan attached to an ice sailcraft stalled on a windless day blows air into the sail that bounces backward upon impact. The boat
moves in the direction of the wind impact force.
An object's weight is properly expressed in units of
newtons.
When Peter tosses an egg against a sagging sheet, the egg doesn't break due to
none of these.
Neglecting air resistance, once a tossed ball leaves your hand
only the force due to gravity acts on it.
When you walk, you push on the floor to the left and the floor
pushes you to the right.
Nellie tosses a ball upward at an angle. Neglecting air resistance, the horizontal component of the initial velocity
remains constant.
A pair of toy freight cars, one twice the mass of the other, fly apart when a compressed spring that joins them is released. The spring exerts the greater force on the
same on each.
If you double the net force on an object, you'll double its
speed.
Two factors that greatly affect air resistance on falling objects are frontal area and
speed.
Compared with falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the
stopping time is longer on the carpet.
When a tennis racquet hits a ball,
the ball hits the racquet.
When a cannonball is fired from a cannon, which undergoes the greater acceleration?
the cannonball
Two identical freight cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple together, and roll away in the direction of
the faster car.
Your weight as measured on your bathroom scale is
the force due to gravity on you.
The winner in a tug-of-war exerts the greatest force on
the ground.
When a constant and sustained upward force acts on a rocket, its acceleration increases mainly because
the mass of the rocket decreases as fuel is burned.
A rock weighs 30 N on Earth and another rock weighs 30 N on the Moon. Which rock has the greater mass?
the one on the Moon.
A karate expert executes a swift blow and breaks a cement block with her bare hand. The magnitude of the force on her hand is
the same as the force applied to the block.
A car traveling at 100 km/h strikes an unfortunate bug and splatters it. The force of impact is
the same for both.
An automobile and a golf cart traveling at the same speed collide head-on. The impact force is
the same for both.
A force of 1 N accelerates 1-kg box at the rate of 1 m/s/s. The acceleration of a 2-kg box by a net force of 2 N is
the same.
A tiny gun made of a strong but very light material fires a bullet more massive than the gun itself. For such a weapon
the target would be safer than the shooter.
When a boxer is moving away from a punch, the force experienced is reduced because
the time of contact is increased.
To say there is no such thing as only one force means
there must also be a corresponding reaction force.
You cannot exert a force on a wall
unless the wall simultaneously exerts the same amount of force on you.
A boulder following a straight-line path at constant velocity has
zero acceleration.
When a falling object has reached its terminal velocity, its acceleration is
zero.
