Integrated Physical Sciences: Section 1, Lessons 5-6

Gravity

an attractive force that acts to pull objects closer to each other

Newton's Law of Universal Gravitation

the force of gravity between any two objects is directly proportional to their masses and inversely proportional to the square of the distance between them

Friction

the force that opposes the motion of an object on which it acts

Static Friction

occurs between two objects touching each other but not moving against each other

Kinetic Friction

the force of friction between two objects moving against each other.

What best describes the net force acting on an object moving in a straight line at a constant speed?

the net force is zero

What is the name of the force that always opposes the motion of an object?

friction

Why is a car more likely to slide if it tries to stop on an icy road than on pavement?

the ice has less friction

When is a force of friction not likely to exist between two objects?

if they are not touching

Why do you need to give a filing cabinet a stronger push to get it to start moving along the floor than to keep it moving?

to overcome the static friction

You can start a fire by rubbing a flint rock with high-carbon steel. What is the force that lets you do this?

kinetic friction

Which factors affect the force of friction between two solid objects?

the types of surfaces and how hard they push against each other

Marie pushes a box across the floor. What causes the box to move?

Marie's force

A car is stuck in the snow and ice. How can it become unstuck?

placing cardboard under the tires to increase friction.

What is the attractive force that exists between any two objects known as?

gravitational force

What is the force that keeps a planet in orbit around the sun?

gravity

Earth's mass is much greater than that of the moon. If you were to stand on the surface of the moon, what would the gravitational force you would experience from the moon be?

weaker than the gravitational force you feel on earth

What would happen if you threw a baseball in interstellar space?

It would continue in a straight line until acted upon by the gravitational force of a star, planet, or other objects.

Which phenomenon is an example of gravity?

The moon orbiting the earth

3 multiple choice options

What is the measure of the amount of gravity acting on an object?

weight

changes in ________ have a greater effect on gravitational force than changes in ______ do

distance, mass

What affects the gravitational force between two objects?

Both the objects' masses and the distance between them

With what force of gravity does Earth pull a bike compared to a truck?

a smaller force

If the distance between two objects is doubled, what happens to the force of gravity between them?

it is decreased

What is the force of gravity exerted by the Earth on you compared to the force of gravity exerted by you on the Earth?

it is the same

linear momentum

the mass of an object times its velocity

the law of conservation of momentum

a scientific law that states that momentum is conserved when two or more objects collide

A bicycle and a train are moving at exactly the same velocity. Which has more momentum, the bicycle or the train?

The train has more momentum.

Now, imagine two identical trains are traveling on parallel tracks. One is moving at 10 km/hr, and the other is moving at 100 km/hr. Which train has more momentum?

The train moving at 100 km/hr has more momentum.

One pool ball collides with another, and the balls move away from one another. Which statement is true if there are no losses to heat or friction?

The total momentum of both balls must be the same before and after the collision.

A ball rolling across a smooth floor gradually slows to a stop. Why does this occur?

Due to friction, the ball gradually loses kinetic energy.

what causes the noise and damage of a car crash?

dispersed kinetic energy

What does the law of conservation of total linear momentum state?

That any momentum lost by one object in a collision will be gained by the other

What is a disadvantage of friction?

Friction reduces the efficiency of engines and other machines by converting parts of their kinetic energy into heat.

A brick is dragged across a concrete floor. Which type of friction acts between the brick and the floor?

kinetic friction

Why is an applied force necessary to keep most objects in the world moving at a constant velocity?

Because a frictional force opposing motion acts on most objects

If you could stop a planet for just an instant and then let it go, what would happen to it?

it would fall into the sun

If the distance between Earth and the sun were decreased, how would the gravitational force between them change?

The gravitational force would increase.

If the mass of Earth were doubled (while keeping its size the same), how much more would you weigh at the surface?

you would weigh the same