CH 2 Lecture Slide: newton's first law of motion- intertia

aristotle’s ideas

natural and violent motion

natural motion

every object in the universe has a proper place, determines by order of earth, water, air, and fire

violent motion

produced by external pushed or pulls on objects

ex: wind on the motion of a boat

Galileo’s discovery

• objects of different weights fall to the ground at the same time in the absence of air resistance

• a moving object needs no force to keep it moving in the absence of friction

force

a push or pull

inertia

• property of matter to resist changes in motion

• depends on the amount of matter in an object (mass)

• the larger the mass, the more inertia, the harder to change its state of motion

newton’s first law of motion

every object continues in a state of rest or of uniform speed in a straight line unless acted on by a nonzero net force

gravity

9.80 m/s²

weight equation

(mass)(9.80 m/s²)

normal force is a

supporting force

frictional force

a reactive force, resists the motion when two surface moving relative to each other

force is a

vector

vector

• quantity whose description requires magnitude and direction

• arrows

• ex: force, velocity, acceleration

scalar

• quantity whose description requires only magnitude

• ex: temperature, speed

net force

the combination of all forces that change an object’s state of motion

the equilibrium rule

• net force is zero

• ∑F = 0

∑F=0 applies to

vector quanities

When you stand on two bathroom scales with one foot on each scale and with your weight evenly distributed, each scale will read

half your weight

equilibrium

a state of no change with no net force acting

static equilibrium

hockey puck at rest on slippery ice

dynamic equilibrium

hockey puck sliding at constant speed on slippery ice

equilibrium test

whether something undergoes changes in motion

A bowling ball is in equilibrium when it

is at rest, moves steadily in a straight-line path

You are pushing a crate at a steady speed in a straight line. If the friction force is 75 N, how much force must you apply?

equal to 75 N

proposed that earth is moving

copernicus

You are riding in a van at a steady speed and toss a coin up. Where will the coin land?

back in your hand