Physics 10: Velocity, Acceleration, and Newton's Laws

A man falling through the air with a parachute on weight 500N. When he opens his chute, he experiences an initial air resistance force of 800N. The net force on the man is:

300N upward

A package falls off a truck that is moving at 40 m/s, horizontally. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is:

40 m/s

An object is in free fall moving in the vertical direction only. At one instant, it is traveling at a speed of 55 meters per second. Exactly one second later, its speed is about.

45 m/s. (acceleration during free fall always = g = 10 m/s^2). 55 m/s - 10 m/s = 45 m/s.

A person is attracted towards the center of the earth by a 500N gravitational force. The force that the earth is attracted toward the person is

500N

A car accelerates at 3 meters per second squared. What is its speed 3 second after the car starts moving from rest?

9 m/s

When throwing a ball upwards, does it take longer for the bullet to go up or to come down?

Come down because of air resistance.

In which case would the bottom of a paper bag carrying groceries is most likely to be ripped open?

When the bag is accelerated upwards.

Disregarding air resistance, objects fall at constant:

acceleration

A truck is moving at constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor below. The rock hits the floor:

exactly below the midpoint of the ceiling.

Among other things, Newton's third says that:

force is always an interaction between two bodies.

Your weight is a measure of your

gravitational attraction to the earth

Mass is a measure of an object's

inertia.

When an object freely falls, its ___________ changes

velocity changes

A 100N bag of groceries is at rest on the ground. How much force is necessary to make the groceries accelerate upward?

Any force of 100N or grater. (to make a net force greater than 0)

What is required to keep an asteroid moving for billions of years out in deep space?

Nothing.

If an object falls with constant acceleration, the velocity of the object must:

continually change by the same amount each second.

If the velocity of a body and its a are oppositely directed then:

the body will slow down.

When a rock thrown straight upwards gets to the exact top of its path, its

velocity is zero and its acceleration is about 10 meters per second squared.

An object following a straight-line path at constant speed has ___ acceleration

0 acceleration

A sack of potatoes weighing 200N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200N, what is the sack's acceleration?

0 meters per second squared (net force = 0, so acceleration = 0)

A falling skydiver of mass 100kg experiences 600N air resistance. What is her acceleration? (For this problem, g=10m/s^2):

0.4g

An apple weighs 1 Newton. When held above your head, the net force on the apple is:

0N. (it is held so it has no acceleration therefore no net force)

An apple weighs 1 Newton. The net force on the apple when it is in free fall is:

1 Newton.

The mass of a dog that weighs 100 Newtons is about:

10 kg. (weight = g*mass)

If you drop an object, after it leaves your hand, it will accelerate downward at a rate of 10 meters per second squared. If you instead throw it downwards, after it leaves your hand its acceleration (in the absence of air resistance) will be:

10 meters per second squared (g)

A Mack truck (big mass) and a VW (small mass) traveling at the same speed have a head-on collision. The vehicle to undergo the greatest change in velocity will be the:

VW (the smaller mass object will experience greater acceleration, so greater change in velocity)

A heavy object and a light object are dropped at the same time from rest in a vacuum (no air resistance). The heavier object reaches the ground:

at the same time as the lighter object

When an object falls through the air, its velocity increases and its acceleration:

decreases (because here we are considering air resistance)

One object has twice as much mass as another object. The first object also has twice as much:

inertia. (inertia is determined by mass)

Concerning gravitational mass and inertial mass...

inertial mass and gravitational mass are the same numbers but different same ideas.

A bullet is dropped from the top of a very tall skyscraper while another bullet is fired downward at the same place. Neglecting air resistance, acceleration is greatest for the

is 10 meters per second squared for each.

An object maintains its state of motion because it has:

mass (mass means inertia, so mass is a good answer)

Newton's Third Law says:

only an even number of total forces (occurring in pairs) exist in the universe

If a body is speeding up, you know its velocity is _______ to its acceleration

parallel

As a ball falls, the action force is the pull of the earth's mass on the ball. What is the reaction to this force:

the pull of the ball's mass on the earth.

A feather and a coin will have equal accelerations when falling in a vacuum (no air resistance) because

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

When a very massive object collides with a small mass, on impact, the forces on each mass are

the same, but the more massive object experiences a smaller acceleration, and the less massive object experiences a greater acceleration.

Newton's second law says that if the acceleration of a body is zero then:

the vector sum of all the forces acting on the body must be zero.