Motion

Describing Motion Motion – when an object changes its position relative to a reference point Distance – how far an object moves Displacement – how far an object moves in reference to the starting point

Rates Any change over time Examples: $7.50/hr Rpm (rotations per minute) Accidents/month Miles/hr m/s

Speed / Velocity Distance traveled per unit of time Speed = distance / time Speed describes the rate of motion Velocity includes the rate of motion and direction

Speed Speed that doesn’t change over time is constant speed Most speeds are non constant average speed Why can’t you run at a constant rate?

Average and Instantaneous Speed Average speed is taken when speed is variable. Average speed = total distance / total time Instantaneous Speed = speed at any given point in time

Distance vs. Time Graphs What does this graph represent? Visual representation of an object’s motion Plot distance on the vertical axis (y-axis) Plot time on the horizontal axis (x-axis) Which is the independent variable? Which is the dependent variable?

AGENDA 1/19/11 You will need your textbook for the assignment today Access Chapter 2 Notes from my public folder Acceleration Discussion Ch. 2 Handout

YOU CAN FEEL ACCELERATION Acceleration is a change in the motion of an object. Positive acceleration – velocity is increasing Negative acceleration – velocity is decreasing Changing an object’s direction is also accelerating YOU CAN FEEL ACCELERATION

Calculating Acceleration Acceleration = change in velocity / time A = ΔV / t (VF – VI) ___________ t

Acceleration Unit of acceleration is m/s2. A velocity vs. time graph Which is the dependent variable? Which is the independent variable?

(+) acceleration has a positive slope (-) acceleration has a negative slope

Where is acceleration experienced at an Amusement Park?

Newton’s Laws of Motion 1st Law- “an object in constant motion remains in constant motion until acted upon by an outside force.” The law of inertia 2nd Law- F = ma 3rd Law- “for every action there is an equal and opposite reaction.”

Forces Force- a push or a pull exerted from one object to another Balanced Forces- forces acting on an object are all equal and in opposite directions Unbalanced Forces- the magnitude and direction of the forces do not cancel one another out Causes motion