Physics Chapter 4 Quiz

The mass of a lamb that weights 110 N is about

11 kg.

Consider the video tutorial you just watched. Suppose that we duplicate this experimental setup in an elevator. What will the spring scale read if the elevator is moving upward at constant speed?

18 N.

An apple at rest weighs 1 N. The net force on the apple when it is in free fall is

1N

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.

An apple weighs 1 N. When the apple is held at rest above your head, the net force on the apple is

0N

A 1-kg mass at the Earth's surface weighs

10 N.

The force of kinetic friction on a sliding object is 10 N. The amount of applied force needed to maintain a constant velocity is

10 N.

What is the net force that acts on a 1-kg freely falling object?

10 N.

What is the weight of a 1-kilogram brick resting on a table?

10 N.

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 10 kg 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

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 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is then

300N upward

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.

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

Suzie Skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on Suzie is then

500 N

A 10-N falling abject 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?

6N

Shake something to and fro and you're measuring its what? Lift it against gravity and you're measuring its what?

Shaking measures mass, whereas lifting measures weight.

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

If the net force on a cart is tripled, the cart's acceleration

is three times as much.

Whenever the net force on an object is zero, its acceleration

is zero.

A kilogram is a measure of an object's

mass.

A car by itself is capable of a certain maximum acceleration. When it tows a twice-as-massive car, its maximum acceleration is

one half

Two factors that greatly affect air resistance on falling objects are frontal area and

speed

Compared to the mass of an apple on Earth, the mass of the apple on the Moon is

the same.

The force required to maintain a constant velocity for an astronaut in free space is equal to

zero

When a falling object has reached its terminal velocity, its acceleration is

zero.

Whenever a net force acts on an object, there is a change in the object's _______.

Velocity.

Which varies with location, mass or weight?

Weight varies with location, but mass does not.

In the string-pull illustration in Figure 4.8, a gradual pull of the lower string results in the top string breaking. Does this occur because of the ball's weight or its mass?

Weight.

Which depends on gravity?

Weight.

What is the condition for an object experiencing free fall?

When gravity is the only force acting on an object, it is in free fall.

A crate sits at rest on a factory floor. Friction between the crate and floor occurs _______.

When the crate is pushed horizontally, whether sliding or not.

When does the proportion form of Newton's second law take the form of an equation?

When units of newtons and kilograms are used for force and mass.

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 10-N falling object encounters 10 N of air resistance. The net force on the object is

0 N.

How does acceleration depend on mass?

Acceleration is inversely proportional to mass.

State Newton's second law of motion.

Acceleration is proportional to net force and inversely proportional to mass.

How does acceleration depend on the net force?

Acceleration is proportional to the net force.

Recall Galileo's Leaning Tower experiment. With negligible air resistance, a heavy and a light object fall

All of the above: With the same increases in speed To the ground in equal times With equal accelerations

Which ball has a greater acceleration as it drops toward the ground, and why?

Ball 1 and Ball 2 have equal acceleration.

Which ball will be traveling faster when it hits the ground?

Ball 1 and Ball 2 will be traveling equally fast when they hit the ground.

Which ball do you predict will reach the ground first?

Both Ball 1 and Ball 2 will reach the ground at the same time.

Two forces, of magnitude 4N and 10N, are applied to an object. The relative direction of the forces is unknown. The net force acting on the object __________.

Cannot have a magnitude equal to 5N.

If Dr. Hewitt applies 3 N of force to keep the block moving at a steady rate, what must be the force of friction, and why?

Equal to 3 N, because the force of friction should exactly balance out the force Dr. Hewitt applies, so that there is no net force acting on the block.

You are dragging a block on a surface with friction at a steady speed of 2 m/s and exert a force of 5 N to do so. What is the force of friction? Why?

Equal to 5 N, because the force of friction should exactly balance out the force Dr. Hewitt applies, so that there is no net force acting on the block.

Does fluid friction vary with speed?

Fluid friction increases as speed increases.

After he gets the block to move, what does Dr. Hewitt do to drag the block across the table at a steady rate?

He continues to apply a steady force.

Give an example of what it means to say mass and weight are proportional to each other?

If the mass doubles, then the weight doubles, too.

As a skydiver gains speed in falling through the air, air resistance _______.

Increases.

In considering proportions, acceleration is _______.

Inversely proportional to mass.

Air resistance on a parachutist at terminal speed _______.

Is greater for a heavier person.

A block of mass 2kg is acted upon by two forces: 3N (directed to the left) and 4N (directed to the right). What can you say about the block's motion?

It could be moving to the left, moving to the right, or be instantaneously at rest.

Use the "Force applied" slider to set the force applied on the elephant to somewhere in the middle of the range. After you have set the "Force applied" slider, do not change it again for this question. How would the acceleration change if the mass of the elephant were increased?

It decreases.

Use the "Mass of elephant" slider to set the mass of the elephant to somewhere in the middle of the range. After you have set the "Mass of elephant" slider, do not change it again for this question. How would the acceleration change if the applied force on the elephant were increased?

It increases.

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

Fill in the blanks: The Standard International unit for mass is _____. The Standard International unit for force is _____.

Mass is kilograms; force is newtons.

In the string-pull illustration in Figure 4.8, a sharp jerk on the bottom string results in the bottom string breaking. Does this occur because of the ball's weight or its mass?

Mass.

A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be __________.

Moving with a constant nonzero acceleration.

The unit of mass is the kilogram, and the unit of weight is the _______.

Newton.

An object's weight is properly expressed in units of

Newtons

What is the approximate weight of a quarter-pound hamburger after it is cooked?

One newton.

The direction of the force of friction on a sliding crate is _______.

Opposite to the direction of sliding.

Which is normally greater: static friction or sliding friction on the same object?

Static friction is normally greater than dynamic friction.

Why does a heavy parachutist fall faster than a lighter parachutist who wears a parachute of the same size?

Terminal speed must be higher to make air drag equal the gravity force for a heavier person.

What is the acceleration of a falling object that has reached its terminal velocity?

The acceleration is 0.

How does the direction of acceleration compare with the direction of the net force that produces it?

The acceleration is in the direction of the net force.

If the mass of a sliding block is tripled while a constant net force is applied, by how much does the acceleration change?

The acceleration is reduced to 1/3 of its original value.

If the mass of a sliding block is somehow tripled at the same time the net force on it is tripled, how does the resulting acceleration compare with the original acceleration?

The acceleration remains the same.

If the net force acting on a sliding block is somehow tripled, what happens to the acceleration?

The acceleration triples.

If two objects of the same size move through the air at different speeds, which encounters the greater air resistance?

The faster object encounters more air resistance.

What two principal factors affect the force of air resistance on a falling object?

The force depends mostly on frontal area and speed.

How does the force of friction for a sliding object vary with speed?

The force of friction is approximately independent of speed.

What general rule can you conclude about the force needed to keep an object in motion at a steady rate?

The force that you need to apply to keep an object moving at a steady rate is equal to the force resisting the motion of the object.

As you increase your push on a stationary crate, will friction on the crate increase also?

The friction force increases and is opposite in direction to your push.

When you push horizontally on a crate that doesn't slide on a level floor, how great is the force of friction on the crate?

The friction force is equal and opposite to your push.

An object cannot remain at rest unless which of the following holds?

The net force acting on it is zero.

If a block is moving to the left at a constant velocity, what can one conclude?

The net force applied to the block is zero.

What is the net force that acts on a 10-N falling object when it encounters 4 N of air resistance? When it encounters10 N of air resistance?

The net forces are 6 N and 0 N, respectively.

The ratio circumference/diameter for all circles is π. What is the ratio force/mass for freely falling bodies?

The ratio is g.

Why doesn't a heavy object accelerate more than a light object when both are freely falling?

The ratio of the weight to mass is the same for all objects in the same locality.

A 1-kg stone and a 10-kg stone have the same acceleration in free fall because _______

The ratio of weight to mass is the same for each.

Once the crate is sliding, how hard do you push to keep it moving at constant velocity?

You push with a force equal to and opposite the dynamic friction 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 you double the net force on an object, you'll double its

acceleration

Which has zero acceleration? An object

all of the above (at rest, in mechanical equilibrium, moving at constant velocity)

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 40 km/h

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

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. The particle with both forces acting

continues at the speed it had when it encountered the second force.