# Forces in Motion II ~ 2/9/12

### 33 terms by ehmssmith

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A condensed version of the quiz review set

### Newton's 1st Law

(Law of Inertia) an object in motion tends to stay in motion & an object at rest stays at rest unless acted upon by an outside force.

### Newton's 2nd Law

The relationship among an object's mass (m), acceleration (a), and an applied force (F), is Force equals mass times acceleration (F= ma).

### Newton's 3rd Law

For every action there is an equal and opposite reaction. Forces act in pairs.

### Newton's childhood

Very sensitive, strong personality and imagination. Went to live at grandmother's farm with apples falling from trees. Einstein's idolized him.

### friction

a force that opposes the motion of 2 Surfaces
static: force acting on objects that are not moving
sliding: force acting on obj. that are sliding
rolling: force acting on obj. that are rolling (duh!)
fluid: force acting on anything contacting liq. and gases

### Microwelds

Microscopic bumps on the surface of objects called _______ are what cause friction.

### Air resistance

The fluid friction experienced by objects falling through the air.

### terminal velocity

the velocity of a falling object when a. r. equals g.

### gravity

Invisible f.o.a. between all objects.
Mass and distance affect gravity

### electromagnetic force

electric and magnetic forces holds negatively charged electrons to the positively charged nuclei of atoms.

### strong nuclear force

a powerful force of attraction holding neutrons and protons together

### weak nuclear force

attractive force responsible for radioactivity- holds the neutron together and is stronger than gravity

### gravitational force

an attractive force that acts between all obj.
mass and distance affect gravity

### The Law of Universal Gravity

Isaac Newton realized that the same forces and the same laws of physics apply everywhere in the universe. So, his law of gravity is called the law of universal gravitation.

Explains why a body falls down to the earth instead of towards the sun or towards a distant planet- the force of the gravity between us and earth is stronger than the force of the sun or distant planets.
Narrow arrows rep. weak gravitational force

### How was Neptune discovered?

while looking for the body whose gravity was affecting the orbit of Uranus.

### projectile motion

the motion of an object after it is given thrust (forward force)

### momentum

the product of an object's mass and velocity. P= MxV

### law of conservation of momentum

momentum does not change it just gets transferred.

### centripetal force

a center-directed force that continuously changes the direction of an object to make it move in a circle; any force that causes an object to move in a circular path

### Horizontal and Vertical motions The 2 components of pro. motion (thanks, Fabiola!)

When the two motions are combined they form a curved path

### Rocket propulsion and Newton's third law

engine thrust (forward force) pushes out rocket/rocket reacts by moving up

### During Collisions...

momentum is conserved (transferred)

### According to Einstein, gravity

_________is not a force but an effect of space itself. Mass causes space to be curved and other bodies are accelerated because of the way they follow this curved space., There is no such thing as the force of gravitation. Gravitation arises when space has curvature around an unseen 4th spatial dimension

### when objects collide

momentum can be conserved, some of the momentum from one object is transferred to the other

### Mass vs. Weight

Mass is how much matter you have; weight is the measured RESPONSE to the pull of gravity.
Weight changes with gravity; mass doesn't change

### 9.8 m/s/s

the gravitational pull on the earth; acceleration in a vacuum on earth with no a.r. until t.v.

### Weightlessness

An object's apparent weight of zero that results when there are no forces pushing up on it

### free fall

when the only force acting on a falling object is gravity

### Horizontal and vertical motion

The two parts of projectile motion. When the two motions are combined they form a curved path

### Centripetal force

the inward force on a body moving in a curved path around another body; a force that causes an object to move in a circle

### Rocket propulsion

the rocket moves forward when gases from the rear of the rocket push it in the opposite direction; , based on Newton's third law of motion.

### Momentum

the product of a body's mass and its velocity
P=MxV

### Conservation of Momentum

momentum transfers from one object to another with the total momentum being conserved; when objects collide, momentum is transferred

Example: