PHY100 - Practice Questions Ch 4
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 in meters per second per second is
0
A 10-N falling object encounters 10 N of air resistance. The net force on the object is
0 N
An apple weighs 1 N. When held at rest above your head, the net force on the apple is
0 N
A falling skydiver of mass 100 kg experiences 500 N air resistance. The acceleration of the skydiver is
0.5 g
A skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of about
0.5 g
A 10-kilogram block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. The acceleration of the block in meters per second per second is
1
An apple weighs 1 N. The net force on the apple when it is in free fall is
1 N.
The mass of a pet turtle that weighs 10 N is about
1 kg
A 1-kg ball is thrown at 10 m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is about
10 N
The force of friction on a sliding object is 10 newtons. The applied force needed to maintain a constant velocity is
10 N.
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 push on a 1-kg brick accelerates the brick. Neglecting friction, to equally accelerate a 10-kg brick, one would have to push with
10 times as much force
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 bag of groceries has a mass of 10 kilograms and a weight of about
100 N
An object released from rest on another planet requires one second to fall a distance of 6 meters. What is the acceleration in meters per second per second due to gravity on this planet?
12
A tow truck exerts a force of 3000 N on a car, accelerating it at 2 meters per second per second. What is the mass of the car?
1500 kg
A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. What is the jet's acceleration in meters per second per second when taking off?
2
A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the magnitude of the net force exerted on the car?
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 in meters per second per second of the car?
220
What horizontally-applied force will accelerate a 400-kg crate at 1 m/s2 across a factory floor against a friction force half its weight?
2400 N
An empty roller-coaster car at an amusement park takes 3 minutes to make its ride from start to finish. Neglecting friction, a fully loaded car would take
3 minutes
A girl pulls on a 10-kg wagon with a constant horizontal force of 30 N. If there are no other horizontal forces, what is the wagon's acceleration in meters per second per second?
3.0
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 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is
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
If you are driving at 20 m/s and slam on your brakes and skid at 0.5 g to a full stop, the skidding time in seconds is about
4
An astronaut on another planet drops a 1-kg rock from rest. The astronaut notices that the rock falls 2 meters straight down in one second. On this planet, how much does the rock weigh?
4 N
A man weighing 800 N stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is
400 N
An object is pulled northward with a force of 10 N and southward with a force of 15 N. The magnitude of the net force on the object is
5 N
An astronaut on another planet drops a 1-kg rock from rest and finds that it falls a vertical distance of 2.5 meters in one second. On this planet, the rock has a weight of
5 N.
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 stopping force acting on the block is about
50 N
A skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on the diver is then
500 N
When a woman stands at rest with two feet on a scale, the scale reads 500 N. When she gently lifts one foot, the scale reads
500 N
A 10-N falling object encounters 4 N of air resistance. The net force on the object is
6 N
A block is dragged without acceleration in a straight-line path 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 rock is thrown vertically into the air. At the top of its path, its acceleration in meters per second per second is
9.8
A 1-kg mass at the earth's surface weighs
9.8 N
A 1-kg rock that weighs 9.8 N is thrown straight upward at 20 m/s. Neglecting air resistance, the net force that acts on it when it is half way to the top of its path is
9.8 N
The human body can, under certain conditions, withstand an acceleration of 10 g. What net force would produce this acceleration of a 50-kg person?
About 5000 N
Which has the greater mass? A) a king-size pillow B) an automobile battery
B) an automobile battery
Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much A) inertia. B) mass. C) volume.
D) all of these
Which has zero acceleration? An object A) at rest. B) moving at constant velocity. C) in mechanical equilibrium.
D) all of these.
Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has the same A) mass. B) volume. C) weight. E) none of these.
E) none of these
If an object of constant mass experiences a constant net force, it will have a constant
acceleration
If the mass of an object does not change, a constant net force on the object produces constant
acceleration
When you stand at rest on a pair of bathroom scales, the readings on the scales will always
add to equal your weight
Hang from a pair of gym rings and the upward support forces of the rings will always
add up to equal your weight.
Neglecting friction, a large block of ice and a small block of ice start sliding down an incline together. The heavier block will get to the bottom
at the same time as the light block
Suppose you're coasting on level ground 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
Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction from the first force. The particle with both forces acting on it
continues at the speed it had when it encountered the second force
A skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration
decreases
A skydiver steps from a helicopter and falls for 5 seconds before reaching her terminal velocity.
decreases
When an object falls through the air, its velocity increases and its acceleration
decreases
An object is propelled along a straight-line path by a force. If the net force were doubled, the object's acceleration would
double
An elephant and a feather fall from a tree through the air to the ground below. The amount of air-resistance force is greater on the
elephant
The newton is a unit of
force
A large and a small person wish to parachute at equal terminal velocities.
get a larger parachute.
An object is propelled along a straight-line path in space by a force. If the mass of the object somehow becomes twice as much, its acceleration
halves.
An object following a straight-line path at constant speed
has zero acceleration
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
If a non-rotating object has no acceleration, then we can say for certain that it is
in mechanical equilibrium
If an object's mass is decreasing while a constant force is applied to the object, the acceleration
increases
A heavy block at rest is suspended by a vertical rope. When the block is accelerated upward by the rope, the rope tension
increases.
One object has twice as much mass as another object. The first object also has twice as much
inertia.
Whenever the net force on an object is zero, its acceleration
is zero.
A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is
its weight
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. Air resistance just before they hit is actually greater for the
lead-filled ball
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 into the air. Because of air resistance, its speed when it returns to its starting level compared to its initial speed is
less
88) A ball thrown straight upward takes 10 seconds to go up and return to the ground. Because of air resistance, the time taken for the ball just to go up is
less than 5 s.
A force is a vector quantity because it has both
magnitude and direction.
A kilogram is a measure of an object's
mass
An object maintains its state of motion because it has
mass
In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the
moon
A ball is thrown vertically into the air. Because of air resistance, its time coming down compared to its time going up is
more
An object's weight may properly be expressed in
newtons
The maximum acceleration of a car while towing a second car twice its mass, compared to no towing, is
one third.
Two factors that greatly affect air resistance on falling objects are the
size and speed of the object
Your weight is
the gravitational attraction between you and the Earth.
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
Strange as it may seem, it is just as hard to accelerate a car on the moon as it is to accelerate the same car on Earth. This is because
the mass of the car is independent of gravity.
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
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.
If less horizontal force is applied to a sliding object than is needed to maintain a constant velocity,
the object eventually slides to a stop
An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the greater mass?
the one on the moon
A feather and a coin will have equal accelerations when falling in a vacuum because
the ratio of each object's weight to its mass is the same
A force of 1 N accelerates a mass of 1 kg at the rate of 1 m/s2. The acceleration of a mass of 2 kg acted upon by a net force of 2 N is
the same
Compared to the mass of a certain object on Earth, the mass of the same object on the moon is
the same
The brakes of a speeding truck are slammed on and it skids to a stop. If the truck were heavily loaded so that it had twice the total mass, the skidding distance would be
the same
The force required to maintain an object at a constant velocity in free space is equal to
zero
When a falling object has reached its terminal velocity, its acceleration is
zero
