PY 131 Chapter 4/5 Conceptual Academy

**Acceleration is directly proportional to the**

net force acting on the object.

**Acceleration is indirectly proportional to the**

mass of the object.

The net force on a jet plane flying at a contant velocity is

zero

When a block is pulled at constant velocity over a surface with a 3 Newton force, the force of friction is

also 3 Newtons

In this lesson, mass is described as the

laziness of matter

In this lesson weight is described as

the force with which an object presses against a supporting surface.

When you pull quickly on a string beneath a suspended ball and it breaks, the concept illustrated is

the ball's inertia.

The greater the net force, the

larger the acceleration.

The direction of acceleration is

always in the direction of the net force.

The unit m/s2 is equivalent to the unit

N/kg

The force due to gravity on a falling object is

mg

The symbol for the gravitational field is

g

**The sky diver who reaches terminal velocity first is the**

girl

Air resistance depends upon

surface area and speed

Whenever a net force acts on an object, there is a change in the object is

velocity

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

opposite to the direction of sliding.

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.

Which depends on gravity?

weight

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

newton

In considering proportions, acceleration is

inversely proportional to mass.

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.

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

increases.

Air resistance on a parachutist at terminal speed

is greater for a heavier person.

When you push against a wall, what pushes back?

The wall pushes back.

A boxer cannot exert much force on a piece of tissue paper suspended in air because

the tissue paper has too little mass to exert as much force on the boxer's fist.

In the apple-pulling-the orange sequence in this chapter, what is the force that accelerates the system across the floor?

Friction between the apple and the floor.

The force that propels a rocket is that provided by

the expelled gas pushing on the rocket.

The team to win in a tug-of-war is the team that

pushes harder on the floor while holding the rope.

When hitting a tennis ball with your racquet, the force on the ball has the same magnitude as the force on the

racquet.

A Volkswagen Bug and a Volvo truck have a head-on collision. Which statement is true.

The magnitudes of both forces are the same.

Two 5-N vectors at an angle of 45degrees to each other have a resultant force of about

7 N

When Nellie Newton dangles by a pair of ropes, each at different angle from the vertical, the rope tension will be greater in the rope having the

least angle

Velocity vector components for a stone tossed in air

are normally at right angles to each other.

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.

Newtons third law of motion is the law of

action-reaction.

Two people standing still pull on a rope held between them. Who pulls harder?

Both pull the same.

In this lesson we considered the system of

Miss Orange, then Mr. Apple, then Miss Orange + Mr. Apple.

The force that accelerated the system of Orange and Apple was

friction by the floor.

For the same punch, a boxer exerts more force on a

punching bag.

For equal weight blocks in this problem, acceleration is

one-half g.

When acceleration occurs, tension in each string is

less than the weight of the hanging block.

If friction were great enough so no acceleration of the blocks occurred, tension in each string would be

equal to the weight of the hanging block.

A horse pulling a cart is also pushed by the

ground.

A rifle has less acceleration than the bullet it fires because of a

greater mass

An object’s measurement in kilograms is a measurement of its

mass

A 4 kg chunk of pure lead, compared to a 2 kg chunk, has the identical

None of these (mass, weight, volume)

Two people are playing tug-of-war on a frictionlesss surface with 12 meters between them. One person has twice the mass of the other. They slide toward each other and just before meeting the heavier person has slid

4 m

A rock tossed upward requires 10 seconds to rise from and fall to the same level. Considering air resistance, its time of rise is

less than 5 s

Considering air resistance, will a lighter or heavier object reach zero acceleration faster when dropped?

lighter

In deep space, a small rock moving at constant speed in a straight line

has zero acceleration

On Planet Z, which has no atmosphere, a 1 kg stone is dropped from rest. One second later it hits the grown 2.5 meters below. The stone's weight on Planet Z is

5 N

Within a vacuum, a coin and a feather fall side by side because

the ratio of each object's weight to mass is the same.

Earth pulls on the moon. Similarly the moon pulls on Earth, evidence that. Earth's gravity tugs on the Moon. Likewise, the Moon's gravity tugs on Earth. This is evidence that

these two tugs comprise an action-reaction pair

A 400 kg box is to be pushed across a floor with an acceleration of 1 m/s per second, while the friction is 1/2 the weight. What force is needed?

2400 N

The net force acting on a 9 N object falling against 3 N of air resistance is

6 N

Not touching the ground, you sit still on a swing. The upward forces on the two ropes of the swing will always

add up to equal your weight

If a bow string pushing an arrow is the action force, then the reaction force is the

arrow’s push against the bowstring

Suspended by a rope a heavy block hangs still. As the block is then pulled upward, the tension in the rope

increases

While skydiving, your velocity of fall increaes, which means your accleration

decreases

A 600 N parachutist experiences an air resistance of 900 N upon opening her chute. The net force acting on her is then

300 N upward

You stand with one foot on a bathroom scale and the other foot on an identical scale. Each scale then indicates

any of the above may be correct (around half)

Earth pulls on a falling ball. The reaction force is the

pull of the ball’s mass on the Earth

Your buddy says the world's strongest boxing champion can't punch a hanging sheet of tissue paper with a force of 100 N. Knowing physics, you

agree that it can’t be done

For an object with no net force acting on it, the acceleration

is zero

An object sliding encounters 10 N of friction. For constant velocity, the needed applied force is

10 N

At terminal velocity, a falling object's acceleration is

zero

On level ground you apply breaks to slow your car from 60 km/h to 40 km/h. Upon quickly releasing the breaks your car tends to

continue moving at 40 km/h

A piece of gold would give you the largest mass if it weighed 1 N on the

moon

On the surface of Earth, a mass of 1 kilogram weighs

9\.8 N

Your weight is

the gravitational attraction force between you and the earth

A 20 kg block and a 2 kg block are falling with no air resistance. The gravitational force on the 20 kg block is

10 times as much

After being thrown upward, a rock reaches the top of its trajectory where the net force acting on it is

equal to its weight

A tree moves at 30 km/s relative to the Sun. A squirrel jumps from a branch on this tree to an acorn on the ground. But taking one second to drop, the acorn should then be 30 kilometers away. We can understand why this reasoning is wrong by looking to Newton's

first law

If an item has two times the mass of another item, then it also has two times the...

inertia

An object sliding at constant velocity is suddenly pushed harder. The object will then...

\n **accelerate in the direction of the applied force.**

Air resistance on something that falls is related to the

size and speed of the object

In order for two different people to parachute down at the same terminal velocities, the larger person must first

have a larger parachute

A 4 kg chunk of pure lead, compared to a 2 kg chunk, has two times as much

all of these

Accelerating a car on a level surface of the Moon is just as difficult as on Earth because

the mass of the car is independent of gravity

On Planet B with no atmosphere, a 1 kg rock held at rest takes 1 second to drop 2 meters to the ground where the rock weighs

4 N

Newtons are a unit of

force

A 100 kg skydiver experiencing 500 N of air resistance will have an acceleration of

0\.5 g

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 car and a mosquito moving with the same speed collide head-on. The force of impact is

1 N

A falling skydiver is pulled down by Earth's gravity. The reaction force is the

the diver pulling the Earth upward.

A 500 N woman standing on a bathroom scale gently lifts one foot. The reading on the scale

remains 500 N

A feather glides off a table and falls to the floor. While falling, its acceleration

in sometimes zero

A 10 N pet frog has a mass of

1 kg

While you're pulled down to Earth by a force of 500 N, the Earth is pulled up to you by a force of

500 N

Considering air resistance, a ball thrown straight up at 15 m/s returns to its starting point at

less than 15 m/s

Being pushed horizontally by 20 N, a 10 kg block encounters 10 N of friction. Its acceleration is thus

1 m/s

An object sliding at constant velocity is no longer pushed as hard. That object will then

eventually slide to a stop

A ball weighing 9.8 N is tossed straight up at 20 m/s. Ignoring air resistance, when the ball is half way up to its greatest height, the net force acting on it is

9\.8 N

A car is accelerated down the road by a force exerted by the

road

The air resistance on a falling bowling ball versus a falling feather is

greater on the bowling ball

With 800 N of air resistance, a falling 100 kg skydiver experiences an acceleration of

0\.2 g

The pull of someone's body downward to Earth is that someone's weight. The opposing reaction is

the person's body pulling on the Earth

Two objects of different densities but the same shape and size are dropped. Considering air resistance, which object hits the ground first?

the heavier

A 600 N man has his weight evenly distributed across two scales. On each scale the reading is...

300 N

A rock on Earth and a rock on the moon each weigh 30 N. The one with a greater mass is

the one on the moon