Speed (s) s= d/t (average speed) Scalar!!!! Velocity (v) v= D/t (average velocity) = (x f – x i )/t Vector!!!! Units: m/s

Practice Jimmy jogs the following path to get to school each day. If it takes Jimmy 25 minutes to get to school, what is his average speed and velocity? 120 m 50 m 60 m 150 m s=d/t s=( )/(25*60) =0.28 m/s v=D/t X: = 220m Y: = 110m =246 m = 246/(25*60) = m/s

Where have seen speed before? SLOPE!!!!!! Slope = rise/run Look at the Units!! = m/s = velocity

Where have seen speed before? What would the equation of this line look like? y = mx + b x = vt + x i What happens if you solve for v? v = (x f – x i )/t Physics is true!!!!!!!!! Replace y with the quantity on Y-axis. Replace x with the quantity on X-axis.

Understanding Graphs of Motion Who is traveling the fastest? Who is going backwards? Who is standing still? Is there anything wrong with E? x (m) t (s) A B C D E

Instantaneous Velocity

Practice Jane is trying to figure out how deep a well is. She invites Jimmy over and pushed him into the well. According to her stop watch, she heard Jimmy’s splash 2 seconds after she saw him hit the water. (The speed of sound in air is 340 m / s ) s=d/t d=s*t d = 340m/s * 2s = 680 m

Practice Jimmy needs to finish his 300 m race with an average speed of 3 m/s. He runs the first 80m at 5 m/s, and the next 100m at 2 m/s. How fast does Jimmy need to run last stretch of the race to complete his goal? s=d/t so t=d/s…. t=300/3 = 100s total time t=d/s 80m/(5m/s) = 16 s t=d/s 100m/(2m/s)= 50 s 16+50= 66s …… = 34 s 300m – 180m= 120 m 120 m / 34 s = 3.5 m/s

Practice Jane is frantically shopping for a well cover. She runs down one aisle (25m long) at 2 m/s. Then another aisle (30m long) at 3 m/s. She finds the cover after sprinting down a third aisle at 5 m/s for 10m. How long does it take Jane to find the cover? Draw a position vs. time graph that describes Jane’s search: t=d/s 25m/(2 m/s) = 12.5 s t=d/s 30m/(3 m/s) = 10 s t=d/s 10m/(5 m/s) = 2 s t = = 24.5 s x t slope=2 slope=5 slope=