Transcript AcaDec - University of Arizona

Science w/ Ms. Hendryx
9/8/11
1. What am I asked for? What units?
2. What do I know? What units do I have to
work with?
3. What do I need to know? What units are
missing?
4. Solve!
There are 8 slurps in a burp, and there are 5
burps in a farkle. 3 farkles are equal to 4
bonks. If I have 2 bonks, how many slurps
do I have?
Force has units of Newtons. A Newton is
defined as (kg*m)/s2. If I have a ball with a
force of 3 Newtons moving with a velocity of
10 m/s for 2 seconds, what is the mass of
the ball?
Position and Velocity
Displacement
Acceleration
Definition
Distance with
direction
Speed with
direction
Change in velocity
with respect to
time
Units
m
(units of distance)
m/s
(units of
speed)
m/s2
(units of velocity
divided by units of
time)
v = v0 + at
Δx = ½(v0 + v)t
Δx = v0t + ½at2
v2 = v02 +2aΔx
What is an object’s acceleration if it begins
at rest and reaches 10m/s in 5s?
What is an object’s final velocity if it begins
at 3m/s and accelerates at 2m/s2 for 4s?
What was the original velocity of an object
that traveled 2m at an acceleration of
5m/s2 and reached a final velocity of 6m/s?
Which equation solves for the time it takes
for a ball to reach
the ground if thrown horizontally at 5m/s
from a height of
25m?
a. -25m = -5m/s(t) + . (9.8m/s2)t2
b. 25m = 5m/s(t) + . (9.8m/s2)t2
c. 25m = 0 + . (9.8m/s2)t2
d. -25m = 5m/s(t) + . (-9.8m/s2)t2
e. 25m = 5m/s(t)
When solving two-dimensional motion problems, the
variable that remains the same in both the x- and ydirections is
a. velocity
b. displacement
c. acceleration
d. time
e. momentum
1. Objects in motion stay in motion, and
objects at rest stay at rest unless a force
is applied. (Constant velocity unless a
force is present)
2. F = ma
3. For every action, there is an equal and
opposite reaction.
GRAVITY: F = mg
g = -9.81 m/s2
FRICTION (only works as opposing force):
Static—before the object starts
moving (block on a ramp)
Kinetic—after the object starts
moving (block on a ramp; air resistance)
NORMAL FORCE:
Supporting force (perpendicular to
surface; book on desk)
You strike a golf ball with 150 N of force, at an angle of 30
degrees above the horizontal. As a result, the golf ball exerts
a. a force of 150 N at an angle of 30 degrees above the
horizontal on your golf club
b. a force of 150 N at an angle of 0 degrees above the horizontal
on your golf club
c. a force of 150 N at an angle of 30 degrees below the
horizontal on your golf club
d. no force on your golf club; otherwise the ball would not move
e. no force on your golf club; otherwise your golf club would fly
backwards
Ignore air resistance effects. A ball is thrown straight
up into the air at 5 m/s. At the highest point in its
trajectory,
a. velocity is zero
b. velocity is constant
c. acceleration decreases
d. acceleration is zero
e. acceleration increases
Draw arrows corresponding to the forces acting on
the blocks:
m