physics ch.4
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
A 1-kg rock that weighs 10 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
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 very top of its path, its acceleration is
10 m/s2
A tow truck exerts a force of 3000 N on a car, which then accelerates at 2 m/s2. 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 when taking off?
2 m/s^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
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
if you are driving at 20 m/s and slam on your brakes and skid at 0.5g to a full stop, the skidding time is about
4 s
Phil stands at rest with both feet on a scale that reads 500 N. When he gently lifts one foot, the scale reads
500 N
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 the ground first?
The heavy man
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 railroad car produces constant
acceleration
if you double the net force on an object, you'll double its
acceleration
A car by itself is capable of a certain maximum acceleration. When it tows a car of the same mass, its maximum acceleration is
one half
A car by itself is capable of a certain maximum acceleration. When it tows a twice-as-massive car, its maximum acceleration is
one third
A force of 1 N accelerates 1-kg box at the rate of 1 m/s2. The acceleration of a 2-kg box by a net force of 2 N is
same
Compared to the mass of an apple on Earth, the mass of the apple on the Moon is
same
Strange as it may seem, it is just as difficult to accelerate a car on a level surface on the Moon as it is here on Earth because
the mass of the car is independent of gravity
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 feather and a coin will have equal accelerations when falling in a vacuum because
the ratio of both the feather's and coin's weight to mass is the same.
a bowling ball and a baseball accelerate equally when falling in vacuum because
the ratio of their weights to mass is the same.
A 1-kg mass at the Earth's surface weighs
10 N
If an apple experiences a constant net force, it will have a constant
acceleration
the newton is a unit of
force
Suzie Skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on Suzie is then
500 N
the human body can withstand an acceleration of 10g under certain conditions. what net force would produce this acceleration for a 50-kg person?
5000 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. in this planet, the rock has a weight of
5N
Neglecting friction, a small and a large block of ice start sliding down an incline together. The larger block reaches bottom
at the same time as the same time as the small block
A heavy ball hangs by a string, with a second string attached to its bottom. a quick pull on the bottom strings breaks the
bottom string
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
A large and a small person wish to parachute at equal terminal velocities. The larger person should
get a larger parachute
a coconut and a bird's feather fall from a tree through the air to ground below. the force of air resistance is
greater on the coconut
If the net force on a cart is tripled, the cart's acceleration
is three times as much
A skydiver steps from a helicopter and falls for a few seconds until terminal velocity is reached. Thereafter, until he opens his parachute, his acceleration
is zero
Whenever the net force on an object is zero, its acceleration
is zero
A 10-N falling object encounters 10 N of air resistance. The net force on the object 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 becomes
0 m/s2
Scotty Skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of about
0.5 g
An apple weighs 1 N. When the apple is held at rest above your head, the net force on the apple is
0N
an apple at rest 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 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 is
1 m/s2
A 10-N block and a 1-N block lie on a horizontal frictionless table. To impart equal horizontal accelerations, we would have to push the heavier block with
10 times as much force
A push on a 1-kg brick accelerates it. Neglecting friction, equally accelerating a 10-kg brick requires
10 times as much force
A 10-kg brick and a 1-kg apple are dropped in a vacuum. The force of gravity on the brick is
10 times more than the force on the apple
A bag of groceries that has a mass of 10 kilograms weighs about
100 N
the mass of a lamb that weights 110 N is abouyt
11 kg
An object released from rest on another planet requires one second to fall a distance of 6 meters. What is the acceleration due to gravity on this planet?
12 m/s2
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^2
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
Nellie 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?
3.0 m/s2
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 300-kg bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is
3000 N
A mobile phone is pulled northward by a force of 10 N and at the same time pulled southward by another force of 15 N. The resultant force on the phone is
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 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
An object's weight is properly expressed in units of
Newtons
Recall Galileo's Leaning Tower experiment. With negligible air resistance, a heavy and a light object fall
all of the above
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
which has greater mass
an automobile battery
at equilibrium on a bathroom weighting scale, the downward pull of gravity on you is balanced by
an upward support force
You drive your car at a constant 60 km/h along the highway. You apply the brakes until the car slows to 40 km/h. If at that moment you suddenly release the brakes, the car tends to
continue moving at 40 km/h
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
Suzie Skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration
decreases
If the mass of a cart is quickly loaded to have twice the mass while a propelling force remains constant, the cart's acceleration
halves
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
A heavy rock and a light rock of the same size are falling through the air from a tall building. The one that encounters the greatest air resistance is the
heavy rock
When the bottom string is pulled slowly in the heavy-ball-and-strings demonstration (Figure 4.8 in your book), tension
in the top string is due to your pull plus the weight of the ball
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
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
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
Two tennis balls fall through the air from a tall building. One of them is filled with lead pellets. The ball to reach the ground first is the
lead-filled ball
a ball is thrown upwards and caught when it returns. compared with its initial speed and in the presence of air resistance, the speed with which it is caught is always
less
a ball is thrown vertically into the air. because of air resistance, its speed when it returns to its starting level compared with its initial speed is
less
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 kilogram is a measure of an object's
mass
If a non-rotating object has no acceleration, then we can say for certain that it is
mechanical equilibrium
A rock is thrown vertically into the air. At the very top of its path the net force on it is
mg
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 the air resistance, it's time coming down compared to its time going up is
more
Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has the same
none of these
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
samel
when you stand at rest with your left foot one bathroom scale and your right foot on a similar scale, each of the scales will
show readings that when added equal your weight.
two factors that greatly affect air resistance on falling objects are frontal area and
speed
Your weight as measured on your bathroom scale is
the force due to gravity on you
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 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 heavy ball hangs by a string, with a second string attached to its bottom. A slow pull on the bottom string breaks the
top string
When a falling object has reached its terminal velocity, its acceleration is
zero
the force required to maintain a constant velocity for an astronaut in free space is equal to
zero
A boulder following a straight-line path at constant velocity has
zero acceleration
