Physics

1
Physics
Acceleration and Gravity
2
SC Standards

• PS 5-3
• Explain how changes in velocity and time affect
  the acceleration of an object.
• PS 5-4
• Use the formula a (vf-vi)/t to determine the
  acceleration of an object.
• PS 5-5
• Explain how acceleration due to gravity affects
  the velocity of an object as it falls.

3
Acceleration Vf Vi t

• A rate of change in velocity
• Positive Acceleration- speeding up
• Negative Acceleration- slowing down
  (deceleration)
• Or, a change in direction
• Relationships
• Acceleration change in velocity / time
• Change in velocity final velocity initial
  velocity
• Unit for acceleration m/s/s
• (meters per second per second)

4
Velocity Time Graphs

• Traveling at a constant speed would look like
  this
• A motion diagram would look like this
• Positive Acceleration would look like this
• A motion diagram would look like this

5
More Velocity Time Graphs

• Negative Acceleration would look like this
• A motion diagram would look like this
• What about a graph with two lines?
• Both lines reach the same speed, but the yellow
  one gets there first, it has greater acceleration.

6

• Remember
• Changes in Speed cause Acceleration.
• Changes in Direction cause Acceleration.

7
Galileo and Gravity

• 1600s (17th century)
• First to propose that all objects fall at the
  same rate (in the absence of air).

8
Law of Universal Gravitation

• Sir Isaac Newton (1600s)
• Any two masses exert an attraction toward each
  other.

9
The Law of Gravitation

• The size of the gravitational force between two
  objects depends on their masses and the distance
  between them.
• Fg G m1m2 Fg force of gravity
• d2 G gravitational constant
• m mass
• d2 distance squared

10
Earth

• Acceleration due to gravitational pull of Earth
  is
• Ag 9.8 m/s/s

11
Learning Checkpoint
12
Now try this

• Look at the graph
• Find the acceleration shown by the green and red
  lines.
• Find the deceleration shown by the blue line.

13
Solution

• The green line shows acceleration of 1 m/s/s
• The red line shows acceleration of 2 m/s/s
• The blue line shows acceleration of -3 m/s/s

14
(No Transcript)