2.3 Physics Falling Objects

Free Fall Read page 60 top on Free Fall Look at figure 14 on page 60

FREE FALL If air resistance is disregarded , all objects dropped near the surface of a planet fall with the same constant acceleration.

Free Fall Acceleration Is constant during upward and downward motion Look at figure 15 on page 61 ( read the paragraph to the left) Look at figure 16 on page 61 (read the paragraph above)

Free Fall Equations You will use the previously learned equations to perform free fall problems. Acceleration due to gravity is g = - 9.81 m/s2 Where you have: a = g = - 9.81 m/s2 Dx = Dy

Vertical Problem A flowerpot falls from a windowsill 25.0 m above the sidewalk. How fast is the flowerpot moving when it strikes the ground? vf2 = vi2 + 2aDx vf2 = (0m/s)2 + 2 (-9.81m/s2)(-25.0m) vf = -22.1 m/s, 22.1 m/s, down

Problem (cont) How much time does a passerby on the street have to move out of the way before the flowerpot hits the ground? a = vf – vi / t or t = vf – vi / a t = -22.1m/s – 0 m/s / -9.81 t = 2.25 s

Free Fall Problem If the initial velocity of the ball is 10.5 m/s when it is thrown upward from a height of 1.5 m, what is the velocity of the ball when it passes this point on the way down? -10.5 m/s

Build a chart A ball is thrown straight up into the air at an initial velocity of 25.0 m/s. Create a table showing the ball’s position, velocity, and acceleration each second for the first 5.00 s of its motion

Equations Use: Vf = vi + at (just change the time) Dy = ½ ( vf + vi ) t just watch your signs Or Dy = vit + ½ at2

Chart t y v a (s) (m) (m/s) (m/s2) 1.00 20.1 +15.2 -9.81 2.00 30.4 +5.4 -9.81 3.00 30.9 -4.4 -9.81 4.00 21.6 -14.2 -9.81 5.00 2.50 -24.0 -9.81

Practice Vertical Problems Review sheet can be totally completed. Activity Test