1. a = g = -9.81 m/s/s a = g = -10 m/s2 2-3 Falling Objects
Gravity - the force of attraction
between all matter.
Gravity – one of the FOUR FUNDAMENTAL
FORCES in nature.
If there is NO AIR RESISTANCE, ALL objects, regardless of mass and size, will fall at the
same constant acceleration. – called FREE FALL
The Acceleration due to Gravity on earth is:
a = g = m/s/s
a = g = m/s2
Hammer vs Feather
Galileo's Falling Objects off Leaning Tower of Pisa
Galileo's Inclined Plane

2. 1. Why did the hammer and the falcon feather hit the ground at the same time on the Moon?
2. What would you predict if you dropped a hammer and a falcon feather on Earth? Would they hit the ground at the same time or at different times? Explain your reasoning.
3. If you couldn't go to the Moon, how could you create a situation on Earth to do this experiment?

3. Freely Falling Objects
Displacement vs time graph

4. Velocity vs time graph Slope of a V vs T graph = Negative acceleration
-10 m/s2

5. And a = g “acceleration due to gravity” = 9.81 m/s2
Equations: Distance traveled using symbol (∆y) by an object after a given amount of time (∆t)
And a = g “acceleration due to gravity” = 9.81 m/s2
∆y = vyi ∆t + ½ g( ∆t )2
When initial velocity = 0 m/s
Then, ∆y = ½ g (∆t )2

6. What goes up must come down
Throwing up a ball: Velocity and Distance
Q: A ball is thrown straight upward and then returns to the Earth. Does the acceleration change during this motion?
A: No
What is the acceleration?
-9.81 m/s2
~ -10/ms2 going up and coming down – g is a force pulling down towards the center of earth

7. Throwing Up a Ball: Velocity VS. Time graph

8. 10
Accel.
(m/s2 )
-10
Vel.
(m/s)
Disp.
(m)
Time (s)

9. 10
Accel.
(m/s2 )
-10
Vel.
(m/s)
Disp.
(m)
Time (s)

10. 10
Accel.
(m/s2 )
-10
Vel.
(m/s)
Disp.
(m)
Time (s)

11. 10
Accel.
(m/s2 )
-10
Vel.
(m/s)
Disp.
(m)
Time (s)

12. 10
Accel.
(m/s2 )
-10
Vel.
(m/s)
Disp.
(m)
Time (s)

13. 10
Accel.
(m/s2 )
-10
Vel.
(m/s)
Disp.
(m)
Time (s)