Glencoe 9th PS Chapter 3 – Forces

# Glencoe 9th PS Chapter 3 – Forces

Question Answer
Newton's second law of motion the net force acting on an object causes the object to accelerate in the direction of the net force
Acceleration of an object is determined by the size of the net force & the mass of the object
acceleration = net force/mass a = F/m
unit of acceleration meters per second squared or (m/s?)
unit of mass kilogram
second law of motion – force kg X m/s? – also called the newton (N)
Newton kg X m/s?
Friction force that opposes motion between two surfaces that are touching each other
Zero acceleration when something doesn't move
Static friction friction between two surfaces that are NOT moving past each other
Sliding friction the force that opposes the motion of two surfaces sliding past each other
Rolling friction friction between a rolling object and the surface it rolls on
Air resistance the force that acts on objects falling through the air
Gravity the force that pulls objects toward Earth
Terminal velocity the highest velocity (speed) that a falling object will reach
Law of gravitation any two masses exert an attractive force on each other- the amount depends on the mass of each & distance apart
Four basic forces gravity, electromagnetic, strong nuclear, weak nuclear
Gravitational acceleration of Earth F = m X 9.8 m/s?Net force or "F" = mass "m" multiplied by 9.8 m/s? (meters per second squared)
What direction is the force of Earth's gravity? It is always downward
Weight is the gravitational force exerted on an object – or – "W"
Weight W = m X 9.8 m/s?Weight or "W" = mass "m" multiplied by 9.8 m/s? (meters per second squared)
Free fall the point at which an object falling to Earth is only influenced by gravity
Why do projectiles follow a curved path? because they have horizontal AND vertical velocities
Centripetal acceleration is acceleration toward the center of a curved or circular path
Centripetal force a force directed toward the center of the circle for an object moving in a circular motion
Newton's third law of motion for every action/force on an object there is an equal and opposite reaction force
The location of what planet was predicted correctly using Newton's laws? Neptune
Momentum the product of an object's mass and velocity
Momentum p = m X vproduct or momentum = mass "m" multiplied by velocity "v"
Newton's second law of motion F = (mv? – mvi)/tNet force "F" = an object's change in momentum divided by the time "t" over which the change occurs
Conservation of momentum a group of objects exerting forces only on each other will equal out – and not lose or gain momentum