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# 2nd Qtr Rev 8th Sci

### Review for Essential Learnings Ch 3, 4, 5, 9 - 8th Grade Science

Newton’s First Law of Motion states: An object at rest remains at rest, an object in motion remains in motion, unless acted on by another force
An object’s resistance to a change in motion Inertia
What causes an object to remain at rest or in motion in the same direction at the same speed? Its inertia
Newton’s 2nd Law of Motion states: An object accelerates when an unbalanced force acts on it.
What is the formula used to calculate Force, based on Newton’s 2nd Law of Motion? F = m * a (m = F/a; a = F/m)
Based on Newton’s 2nd Law of Motion, as the Force exerted on an object increases, its acceleration increases
Based on Newton’s 2nd Law of Motion, are Force and acceleration directly or inversely proportional? Directly proportional. As one increases, the other decreases.
Based on Newton’s 2nd Law of Motion, as mass and acceleration directly or inversely proportional? Inversely proportional. As one decreases, the other increases.
The SI unit for Force is N (Newtons) or kg*m/s2
The SI unit for mass is g(grams) or kg (kilograms)
The SI unit for acceleration is m/s2
Define Mass the amount of matter in an object
Define Weight the gravitational force exerted on an object.
How do Mass and Weight differ? The mass of an object remains the same, but its weight changes depending on the amount of gravitational force acting on it.
Newton’s 3rd Law of Motion states: For every action (force) there is an equal and opposite reaction (force)
Because of Newton's 3rd Law, we know if a rocket's boosters fire to the left, the rocket will move to the Right (in the opposite direction).
This is the product of mass and velocity: Momentum
The formula for momentum is p = m*v
In Science, the variable used for momentum in NOT m, but p
The unit for momentum is kg*m/s
Law of Conservation of Energy states Energy can never be created or destroyed, but it can change forms.
When two objects collide, their momentum may be transferred, but not gained or lost.
In pool a cue ball hits a green ball, causing it to move. Use the Law of Conservation of Energy to explain what has happened. The cue ball loses momentum. It is transferred to the green ball which gains momentum, and moves.
Resources that can be easily replaced in a short period of time Renewable resources
Resources that cannot be replaced, or can only be replaced over a long period of time. Nonrenewable resources
Name a renewable resource Wood, water, air, sunlight, hydrogen
Name a nonrenewable resource fossil fuels like gas, oil, petroleum, coal; uranium
What is the scientific definition of work? Work occurs ONLY when a force causes an object to move.
What is the formula for Work? W = F*d (Work equals the Force applied to an object times the distance it moves.)
What is the SI unit for both Work and Energy? J (Joule) or N*m (Newton meter)
Potential energy is Stored energy
Kinetic energy is the energy of motion
PE = m * g * h is the formula for Potential energy
A pendulum has the most potential energy before the weight is released from its highest point
KE = 1/2m * v is the formula for Kinetic energy
A pendulum has the most kinetic energy at the bottom of its swing
Machines make work easier by increasing the force applied to an object AND/OR the distance over which a force is applied
Machines make work easier by changing the speed or direction of the force
Grooved wheel with a rope pulley
Incline plane spiraling around a post Screw
Bar that pivots on a fulcrum lever
Ramp or sloping surface used to lift incline plane
2 wheels of different sizes that rotate together wheel and axle
Double incline plane used for cutting or prying. Wedge
Lever with the fulcrum in the middle 1st Class
Lever with the fulcrum at the end, resistance in the middle, and effort at the other end 2nd Class
Lever with the fulcrum at the end, effort in the middle, resistance at the other end. 3rd Class
What type of lever is a hammer pulling a nail? 1st Class
What kind of lever is a wheelbarrow? 2nd Class
What kind of a lever is a crane? 3rd Class
What kind of a machine is a doorknob? wheel and axle
What kind of machine is a pencil sharpener? wheel and axle; wedge
What kind of machine is a pair of scissors? Wedge; 1st class lever
What kind of machine is a ramp? incline plane
What kind of machine is a flag pole? Pulley
What kind of machine is a screwdriver? wedge; 1st class lever
What is the SI unit for mass, and how do we measure it? grams (or kg); balance
What is the SI unit for weight, and how do we measure it? Newtons (N); spring scale
Created by: judi829