Motion S8P3. Students will investigate relationship between force, mass, and the motion of objects. a. Determine the relationship between velocity and acceleration.

Measuring Motion Motion Speed & Velocity Acceleration

Motion Motion is when an object changes position over time relative to a reference point. Problem: Is your desk moving? We need a reference point... a nonmoving or moving point from which motion is measured

Motion Superman Example The speeding bullet is a moving reference point to Superman’s motion. The tall building is the non-moving reference point when Superman leaps.

Motion Motion Change in position in relation to a reference point.

Motion Problem: You are a passenger in a car stopped at a stop sign. Out of the corner of your eye, you notice a tree on the side of the road begin to move. What’s the problem? You have mistakenly set yourself as the reference point.

s d t Speed Speed rate of motion distance traveled by an object in a given amount of time Write Formula

Speed Instantaneous Speed speed at a given instant Average Speed Write Formula http://www.physicsclassroom.com/mmedia/kinema/trip.cfm

Speed Problem: A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried? It depends on the storm’s direction!

Velocity Velocity speed of an object in a given direction changes when speed and/or direction changes Examples: The car’s velocity was 104 km/h N (about 65 mph N). John’s velocity was 1 m/s S (about 2.2 mph S) The runner’s velocity was 37 km/h W (about 23 mph W).

Graphing Motion slope = speed steeper slope = straight line = * 07/16/96 Graphing Motion Distance-Time Graph A B slope = steeper slope = straight line = flat line = speed faster speed constant speed no motion *

Graphing Motion Who started out faster? A (steeper slope) Distance-Time Graph A B Who started out faster? A (steeper slope) Who had a constant speed? A Describe B from 10-20 min. B stopped moving Find their average speeds. A = (2400m) ÷ (30min) A = 80 m/min B = (1200m) ÷ (30min) B = 40 m/min

t a Acceleration Acceleration the rate of change of velocity vf - vi t Acceleration the rate of change of velocity change in speed and/or direction Write Formula a: acceleration vf: final velocity vi: initial velocity t: time

Acceleration The velocity can change even when the speed is constant! Examples: 25 m/s S  25 m/s E 55 m/s W  20 m/s W

Acceleration Positive acceleration “speeding up” Ex. 5 km/h  25 km/h Negative acceleration (Deceleration) “slowing down” Ex. 25 km/h  5 km/h

Acceleration

Graphing Motion Distance-Time Graph Acceleration is indicated by a curve on a Distance-Time graph. Changing slope = changing velocity

Graphing Motion slope = acceleration Speed-Time or Velocity-Time Graph slope = acceleration “+” velocity = speeds up “-” velocity = slows down Straight line = constant acceleration flat line = constant speed

Graphing Motion Specify the time period when the object was... Speed-Time or Velocity-Time Graph Specify the time period when the object was... slowing down 5 to 10 seconds speeding up 0 to 3 seconds moving at a constant speed 3 to 5 seconds not moving 0 & 10 seconds