Things to discuss for unit I
Get out your
Yellow packet
Equation sheet
Lab manual
Chapter 2
Assignment from SUB DAY
Page 38 questions 2.3.4.6.8.9
By definition, if an object has a
constant velocity, then both the
object's speed and its direction of
motion are constant. Therefore the
object CANNOT have a varying speed if
its velocity is constant.
When an object moves with constant
velocity, its average velocity over any
time interval is exactly
equal to its instantaneous velocity at
all times
Yes. A car that had the greatest overall
velocity throughout the race could
falter and be pushed across the finish
line while another car with a nervous
driver could finally decide to put the
petal to the metal at the end.
The acceleration of both the motorcycle and the bicycle
are the same, since the same change in
velocity occurred during the same time interval.
If you do a further calculation, you will find that the
distance traveled by the motorcycle during the
acceleration is 17 times the distance traveled by the
bicycle.
The velocity of an object can be negative when its
acceleration is positive. If we define the positive
direction to be to the right, then an object traveling to
the left that is having a reduction in speed will
have a negative velocity with a positive acceleration.
If again we define the positive direction to be to the
right, then an object traveling to the right that is
having a reduction in speed will have a positive velocity
and a negative acceleration.
If north is defined as the positive direction, then an
object traveling to the south and increasing in
speed has both a negative velocity and a negative
acceleration. Or, if up is defined as the positive
direction, then an object falling due to gravity has both
a negative velocity and a negative
acceleration.
The first 20 meters of a 100-meter dash are covered in 3 seconds by a sprinter who
starts from rest and accelerates with a constant acceleration. The remaining 80 meters
are run with the same velocity the sprinter had after 3 seconds.
a. Determine the sprinter's constant acceleration during the first 3 seconds.
b. Determine the sprinters velocity after 3 seconds have elapsed.
c. Determine the total time needed to run the full 100 meters.
d. Sketch a p-t graph that illustrates this problem.
. Determine the velocity v of the object at the end of each 5-second interval.
Assume the initial velocity was 2 m/s.
Plot a p-t graph from this information.
Time (s)
6
12
18
21
Displacement from starting
position (m)