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Unit 4 6th Grade
Forces and Motion
Term | Definition |
---|---|
distance | the length between two places |
position | the location of an object compared with things around it |
motion | a change in an object's position compared to fixed objects around it |
speed | how fast an object's position changes with time at any given moment |
velocity | a description of a moving object's speed and direction |
acceleration | a change in the velocity of an object over time |
force | a push or pull exerted by one object on another, possibly causing a change in motion |
contact force | a force that is exerted only when objects are touching |
noncontact force | a force exerted when objects are not touching |
net force | the combination of all forces acting on an object |
balanced forces | forces that act together on an object without changing its motion |
unbalanced forces | forces that do not cancel each other out and that cause an object to change its motion |
gravity | the force of attraction among all objects |
friction | a force that opposes the motion of an object in contact with a surface |
air resistance | the force that opposes the motion of an object through a gas |
elastic force | a force exerted by a material when it is stretched or compressed |
tension force | a pulling force applied to an object that can make an object stretch |
Newton's first law of motion | a physical law stating that an object at rest tends to stay at rest and an object moving in a straight line at a constant speed tends to continue moving that way |
Newton's second law of motion | a physical law that states that an object's acceleration depends on the object's mass and the amount of net force applied to it |
Newton's third law of motion | a physical law that states that for every action there is an equal and opposite reaction |
action force | the initial push or pull of one object on another object |
reaction force | the push or pull of a second object back on the object that started the push or pull |
inertia | tendency of an object to keep moving or remain at rest unless an unbalanced force acts upon the object |