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# Newton's 3rd Law

### questions

Question | Answer |
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State Newton's 3rd Law of Motion | For every action there is an equal and opposite reaction |

How does a balloon filled with air illustrate Newton's 3rd law? | When the air is let out of the balloon, the air moves downward and the balloon moves upward |

In Newton's 3rd law there is always two forces--action force and a reaction force. True or False | True |

Action and reaction forces are equal in ________and opposite in _________. | equal in strength and opposite in direction |

When swimming, you push the water backward--call this the action force. What is the reaction force? | the water pushing you forward |

A car accelerates along a road. Strictly speaking, what is the force that moves the car? | The road pushes the car along |

Your weight is the result of the gravitational force of the earth on your body. What is the corresponding reaction force? | Your body pulling up on the earth |

If a bicycle and a massive truck have a head-on collision, upon which vehicle is the impact force greater? Which vehicle undergoes the greater change in its motion (or greater acceleration)? | same force because the collision is an interaction between two forces; the bike has the greater acceleration because it has the smaller mass |

Use Newton's 2nd law to explain that for a give force the acceleration will always be greater for the object with the smaller mass | The equation shows that acceleration and mass are inversely related. |

A leaf weighting 5 grams falls from a tree at a rate of 2 m/s. What is the force of the leaf hitting the ground in newtons? | 0.01 N |

A car strikes a brick wall and the impact was 5000 N. If the car weighted 100 kg, how fast was it moving in m/s? | 50 m/s |

A car strikes a brick wall and the impact was 5000 N. The car was traveling at 25 m/s. How much did it weigh in kg? | 200 kg |

If you hit a wall with a force of 200 N, how much force is exerted on you? | 200 N |

If you walk on a log that is floating in the water, the log moves backward. Why? | The reaction force is in the opposite direction |

Why is it easier to walk on a carpeted floor than on a smooth, polished floor? | One can exert a greater horizontal force on a carpet that a polished floor because the greater friction force which in turn provides a greater reaction force to provide traction for walking |

Calculate the acceleration of a 2000 kg single-engine airplane just before takeoff when the thrust of its engine is 500 N. | 0.25 meters per second squared |

What are the action and reaction forces of a falling boulder? | action force: earth exerting a force on the boulder reaction force: boulder simultaneously exerting a force on the earth |

An object in space tends to travel in a straight line at constant speed unless what happens? | Acted upon by an unbalanced force |

___________causes acceleration. | Force |

A horizontal force of 100 N is required to push a crate across a factory floor at a constant speed. What is the net force acting on the crate? What is the force of friction acting on the crate? | Zero (a = 0); 100 N |