Download Unit 4 vocabulary - Riverdale Middle School

Unit 4: Forces and Motion
1. distance – length between two places.
2. position – an object’s location compared to other things.
3. motion – a change in an object’s position compared to a fixed object.
4. apparent motion – when things appear to an observer to be moving but are not actually changing
position.
5. speed – how fast an object’s position changes with time at any given moment. Speed is calculated by
dividing the distant traveled by the time taken to travel. S = d/t
6. average speed – a moving object is the total distance traveled divided by the total amount of time.
7. velocity – a description of a moving object’s speed and direction.
8. acceleration – a measure of the change in velocity during a period of time. An object accelerates when
its velocity changes as a result of increasing speed, decreasing speed, or a change in direction.
9. force – Any push or a pull on an object.
10. contact force – is a force that is applied when two objects touch.
11. noncontact force – A force that one object can apply to another object without touching.
12. net force – The combination of all the forces acting on an object.
13. balanced forces – forces acting on an object that combine and form a net force of zero.
14. unbalanced forces – Forces acting on an object that combine and form a net force that is not zero.
15. gravity – is an attractive force that exists between all objects that have mass.
16. friction – a force that opposes the motion of an object.
17. static friction – the force between the surfaces of two solid objects that keeps the objects from
moving.
18. sliding friction – the force that opposes the sliding of an object over a surface.
19. rolling friction – is what opposes the motion of a wheel turning along a surface.
20. fluid friction – friction between a surface and any material, such as water or air, that flows.
21. air resistance – fluid friction between a surface and air
22. elastic force – the force exerted by a material when it is stretched or compressed.
23. tension force – is a pulling force applied to an object that can make the object stretch.
24. compression force – is a squeezing force applied to an object that can make an object shrink.
25. normal force – a force exerted by an object that is perpendicular to the surface of the object.
26. Newton’s first law of motion – states that an object at rest tends to stay at rest, and an object in
constant motion tends to stay in motion, unless acted upon by an unbalanced force.
27. Newton’s second law of motion – states that acceleration depends on the object’s mass and the
amount of net force applied to it. a = F/m.
28. momentum – The combination of the mass and the speed of an object.
29. Newton’s third law of motion – when one object exerts a force on a second object, the second
object exerts an equal force in the opposite direction on the first object. “For every action force, there is an
equal and opposite reaction force.”
30. action force – the push of the first object on the second
31. reaction force – the push of the second object back on the first object.
32. inertia – the tendency of a moving object to keep moving in a straight line.