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# 2nd Qtr Rev 8th Sci

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

Question | Answer |
---|---|

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