1. Chapter 10
Motion

2. Section 1: Measuring Motion
Motion – when an object changes its position relative to a reference point
Distance – how far an object has moved
Displacement – distance and direction of an object’s change of position from a starting point

4. Section 1: Measuring Motion
Speed – distance an object travels per unit of time
Rate – any change over time
Calculation for speed:
speed = distance/time
SI unit for speed is meter per second or m/s

5. Section 1: Measuring Motion

6. Section 1: Measuring Motion
Speed that doesn’t change over time –constant speed
Speed is usually not constant; usually an object has changing speed.
Average speed – speed of motion when speed is changing:
speed = total distance/total travel time
Instantaneous speed – speed at any given point in time

7. Section 1: Measuring Motion
A distance – time graph displays motion of an object over time.
1. Plot distance on a vertical axis.
2. Plot time on a horizontal axis.
Slope = velocity
Velocity – speed and direction of an object’s motion

8. Section 1: Measuring Motion

10. Section 1: Measuring Motion

11. Section 2: Acceleration
Acceleration—change in velocity’s rate
Positive acceleration—speed is increasing.
Negative acceleration—speed is decreasing.
When an object changes speed and/or direction, it is accelerating.

13. Section 2: Acceleration
Calculating acceleration
1. Acceleration = change in velocity/time
2. Change in velocity = final velocity – initial velocity
Acceleration can have a negative sign
3. SI Unit for acceleration—meters per second squared
a = m/s2

17. Section 2: Acceleration
Acceleration can be graphed in a Velocity – time graph
Velocity on y – axis
Time on the x – axis
Slope = acceleration

18. Section 2: Acceleration
Positive acceleration – positive number with a positive slope on a velocity-time graph
Negative acceleration – negative number with a negative slope on a velocity-time graph
Constant velocity – zero slope – flat line

21. Chapter 10.3
Motion and Force

22. Motion and Force
Force - a push or pull that one body applies to another
A force can cause an object’s motion to change.
Cause a change in acceleration and velocity
When two or more forces combine at the same time, they create a net force.
Acceleration is in the direction of the net force.

27. Motion and Force
Balanced forces are equal in size and opposite in direction.
Does not cause motion.
Forces cancel each other out.

28. Motion and Force
Unbalanced forces are unequal in size and / or are not in the same direction.
Causes motion
A net force is created

30. The Force of Friction
Friction – force that opposes motion between two surfaces that are touching each other
Microwelds, areas where surface bumpers stick together, are the source of friction.
Friction opposes motion.

32. The Force of Friction Two types of friction
Static Friction – Friction between two surfaces that are not moving past each other.
Kinetic Friction – Friction between two surfaces that are moving past each other.
Static friction is greater than kinetic friction

34. The Force of Friction Two types of Kinetic friction
Sliding friction – force that opposes the motion of two surfaces sliding past each other.
Rolling friction – Friction between a rolling object and the surface it rolls on.
Force usually less than sliding friction.
Cars could not move with out this type of friction.

35. The Force of Friction
Fluid Friction – force created by the resistance of a fluid.

36. Friction and Motion Harmful Friction can be reduced by 4 ways:
Lubricants – substance that reduces friction.
Ball bearings – creates rolling friction that is less than sliding friction.
Make surface smoother – reduces microwelds
Make more streamline – reduces fluid friction.

38. Friction and Motion Helpful friction can be increased by:
Make surface rougher – increases microwelds
Add mass to increase weight