# Kinematics

Document Sample

```					Engineering Physics: Mechanics

Michael Balogh
Motion diagrams

Represent the position of an object at different (usually equal)
times

1            2            3            4           5
Motion diagrams

1   2
3
4

5

Represent the position of an object at different (usually equal)
times
Example
At which time (or times) do the two balls have the same speed?

1   2
3
4

5

1           2            3           4            5
Describing Motion
Motion Diagram:

x(t)
x(t) graph:
Position (x)

Time (t)
Examples
Sketch motion diagrams and x(t) graphs for the following:

1. A cart at rest.
2. A cart moving with constant velocity. What happens if you
change the velocity? The starting point?
3. Throw a ball in the air. How does the motion change? What
happens if we change the definition of “positive” in our
coordinate system?
4. Throw a ball in the air and catch it again. What is it’s
displacement? Average velocity?
Exercises: Sample 2.1
You drive along a straight road at 70 km/h. After traveling 8.4 km,
you run out of gas and are forced to walk for 30 min, traveling
another 2.0 km (in the same direction) to the nearest gas
station.

a) What is your overall displacement from the beginning of your
drive to your arrival at the gas station?

b) What is the time interval Dt from the beginning of your drive to

c) What is your average velocity from the beginning of your drive
to your arrival at the station?

d) Suppose that to pump the gasoline, pay for it, and walk back to
the truck takes you another 45 min. What is your average speed