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# Math of Mechanics

### 2013 Chapter 3 8th grade Science

Mechanics the study of motion
What does a scalar quantity tell us? Scalar quantities tell size OR magnitude of the thing measured
What does a vector quantity tell us? A vector quantity has both magnitude and direction.
Which of these quantities is a scalar quantity, distance or displacement? Distance is scalar; displacement is vector
Which of these quantities is a vector quantity, Speed or velocity? Velocity is vector; speed is scalar
What are some other vector quantities? Acceleration, force, and momentum
Define Distance How far an object has moved
Define Displacement Distance and direction of an object from its starting point
Define Speed The distance an object moves per unit of time
Velocity Distance and direction an object moves per unit of time
Average speed The average over time when speed is changing
Instantaneous speed Speed at any given moment in time like on your speedometer in the car
Constant speed Speed that is not changing or is staying the same
Acceleration Speed that is increasing or getting faster
Deceleration Negative acceleration or speed that is decreasing/slowing down
Define Force Any push or pull on an object
State Newton’s First Law of Motion When there is no unbalanced force on an object, objects at rest stay at rest and objects moving keep moving at the same speed in the same direction
State Newton’s Second Law of Motion When an unbalanced force acts on an object it accelerates
What did Galileo determine about the rate of falling objects? All objects fall at the same rate if there is little or no air resistance
What is the acceleration of gravity at the earth’s surface? 9.85 m/s2
What are 5 differences between mass and weight? Mass is the amount of matter in something and weight is the pull of gravity. Mass is measure on a balance in g or kg and weight is measured on a spring scale in N. Mass cannot change or be zero and weight can.
What is momentum? Momentum is the product of mass and velocity
How do we calculate it? p(momentum) = m(ass) * v(elocity)
Be able to calculate using the formula for Force F = m* a
Be able to calculate using the formula for momentum p = m * v
Advanced only: What is Impulse? Force times time equals impulse
Advanced only: Relate Impulse to momentum Impulse is equal to the change in momentum.
Advanced only: How does this relate to building safer cars? When momentum changes quickly, Force can be minimized by extending the time it acts. Air bags, seat belts, and bumpers which crumple all work to allow extra time between the Force and its impact in a collision.
Created by: judi829