2 Newton’s First Law Newton’s First Law of Motion An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force.motionconstant velocitynet force
3 A. Motion Problem: Is your desk moving? We need a reference point... nonmoving point from which motion is measured
4 A. Motion Motion Change in position in relation to a reference point.
5 A. MotionProblem: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 forward.You have mistakenly set yourself as the reference point.
6 v d t B. Speed & Velocity Speed rate of motion distance traveled per unit time
7 B. Speed & Velocity Instantaneous Speed speed at a given instant Average Speed
8 B. Speed & Velocity 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!
9 B. Speed & Velocity Velocity speed in a given direction can change even when the speed is constant!
10 t a C. Acceleration Acceleration the rate of change of velocity vf - vitAccelerationthe rate of change of velocitychange in speed or directiona: accelerationvf: final velocityvi: initial velocityt: time
11 C. Acceleration Positive acceleration “speeding up” Negative acceleration“slowing down”
12 t d v D. Calculations d = 100 m v = d ÷ t t = 20 s Your neighbor skates at a speed of 4 m/s. You can skate 100 m in 20 s. Who skates faster?GIVEN:d = 100 mt = 20 sv = ?WORK:v = d ÷ tv = (100 m) ÷ (20 s)v = 5 m/sYou skate faster!vdt
13 t a D. Calculations a = (vf - vi) ÷ t t = 3 s A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration?GIVEN:vi = 10 m/st = 3 svf = 32 m/sa = ?WORK:a = (vf - vi) ÷ ta = (32m/s - 10m/s) ÷ (3s)a = 22 m/s ÷ 3 sa = 7.3 m/s2avf - vit
14 t d v D. Calculations v = 330 m/s t = d ÷ v d = 1km = 1000m Sound travels 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for you to hear it?GIVEN:v = 330 m/sd = 1km = 1000mt = ?WORK:t = d ÷ vt = (1000 m) ÷ (330 m/s)t = 3.03 svdt
15 t a D. Calculations t = ? t = (vf - vi) ÷ a t = (0m/s-30m/s)÷(-3m/s2) How long will it take a car traveling 30 m/s to come to a stop if its acceleration is m/s2?GIVEN:t = ?vi = 30 m/svf = 0 m/sa = -3 m/s2WORK:t = (vf - vi) ÷ at = (0m/s-30m/s)÷(-3m/s2)t = -30 m/s ÷ -3m/s2t = 10 savf - vit
16 E. Graphing Motion slope = speed steeper slope = straight line = *07/16/96E. Graphing MotionDistance-Time GraphABslope =steeper slope =straight line =flat line =speedfaster speedconstant speedno motion*
17 E. Graphing Motion Who started out faster? A (steeper slope) Distance-Time GraphABWho started out faster?A (steeper slope)Who had a constant speed?ADescribe B from min.B stopped movingFind their average speeds.A = (2400m) ÷ (30min) A = 80 m/minB = (1200m) ÷ (30min) B = 40 m/min
18 E. Graphing MotionDistance-Time GraphAcceleration is indicated by a curve on a Distance-Time graph.Changing slope = changing velocity
19 E. Graphing Motion acceleration slope = +ve = speeds up Speed-Time Graphacceleration+ve = speeds up-ve = slows downslope =straight line =flat line =constant accel.no accel. (constant velocity)
20 E. Graphing Motion Specify the time period when the object was... Speed-Time GraphSpecify the time period when the object was...slowing down5 to 10 secondsspeeding up0 to 3 secondsmoving at a constant speed3 to 5 secondsnot moving0 & 10 seconds