Speed and Velocity

______________ are quantities that need direction and __________________.  They will always have a ________   or ________________ sign to show __________________.

Conversely, ________________ are quantities that do NOT need direction.  They will never have a ________. 

We talk about two types of speed:

2.     __________________________ speed = speed at any instant. 

To find the instantaneous speed, you find the ________________ and discard the __________________. 

A Displacement-time graph of no motion looks like this:

The Displacement-time graph of constant velocity looks like this:

The Displacement-time graph of acceleration looks like this:

The __________ of a Displacement-time graph = the __________________________  _______________ at that time. 

The Displacement-time graph of this motion:

looks like:

2.4 Acceleration

How quickly or slowly something changes its velocity is ______________________. 

Acceleration can occur in 3 ways:

1.     ________________  ____

2.     ________________  ____

3.     ________________  __________________

When velocity and acceleration are in the same direction, things __________  ____.  When velocity and acceleration are in opposite directions, things  ________  ________. 

On a Displacement-time graph, accelerations are ____________. 

Make a Displacement-time graph for this motion:

When an object is in free “fall”, it is only affected by ________________. 

This rarely occurs because of ______  ____________________. 

The term free “fall” is deceiving because an object could be going ____ and still be in free fall since it is still only affected by ____________. 

When an object free “falls”, it accelerates at ______  _______.

I.  You drive a beat up pickup truck down a straight road for 5.2 miles at 43 mph, at which point you run out of fuel.  You walk 1.2 miles further, to the nearest gas station, in 27 min (= .450 hours).  What is your average speed for the time you started your truck to the time you arrived at the station? 

s_avg = distance traveled

          time elapsed

Suppose you carry the fuel back to the truck, making the return trip in 35 min.  What is your average speed for the full journey, from the start of driving the truck to your arrival back at the truck with the fuel?

II.  A homing pigeon is released under the center of the Gateway to the West Arch in St. Louis.  What is its average velocity if i) it travels 50 km due east from the arch for one hour?  ii) if instead it travels 50 km due west from the arch for one hour?  iii) if it starts 10 km east of the arch, travels to 20 km due east of the arch, and then travels to 30 km due west of the arch in one hour (assuming straight-line flight)? 

V_avg = final position – initial position

final time – initial time

What would be the average speed in each of these cases?

s_avg = distance traveled

          time elapsed

III.  The next four questions go along with this information:

A rock, dropped from rest near the surface of an atmosphere-free planet, attains a speed of 35.0 m/s after falling 11.0 meters.

What is the magnitude of the acceleration due to gravity on the surface of this planet?

 How long did it take the object to fall the 11.0 meters mentioned?

How long would it take the object, falling from rest, to fall 16 m on this planet?

Determine the speed of the object after falling from rest through 16 m on this planet.

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