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Name:
Physical Science Packet 5.3
Net Force: Fnet=ma
Test and Packet Due on Fri 2/20!
Tutoring: Wed-Fri 3:20-4:20
Period:
Questions? Text or Email Mr. Barnhart
901-654-7797
barnhart.melrose@gmail.com
barnhartmelrose.weebly.com
Learning Targets
Monday: I can
.
Tuesday: I can
.
Wednesday: I can
.
Thursday: I can
.
Friday: I can dominate the quiz.
A1.
Write the symbol AND name of the quantity described
a.
how fast an object is moving
b.
how much an object’s speed changes each second
c.
how long (seconds) an object was moving
d.
how far an object moved
e.
how much “stuff” (protons, neutrons, electrons) an object is made of
f.
extra force in a direction
g.
pull by a rope, cable…etc
h.
resistive force due to moving through air
i.
force due to contact with a hand, ground … etc
j.
active push off surface (along the surface)
k.
active push off the air
l.
gravitational pull of the earth
s
speed
m. resistive force due to moving across a surface
n.
measurement of the roughness of surfaces (difficulty for sliding)
o.
measurement of ability to catch air (area & shape)
p.
describes the direction an object is moving
A2. What synonym do we use for “net” in our definition of net force?
A3. If all the forces on an object are balanced, what can the object be doing? What law of physics is this?
A4. Explain how to determine whether an object’s speed will increase or decrease based on the net force and velocity.
A5. What equation relates forces to motion? What law of physics is this?
A6. A fan and masses are placed on a cart on a flat track. Describe two ways to increase the fan-cart’s acceleration. Which
one of Newton’s Laws does this exemplify?
Bellwork Answers. Always explain why!!!
bellwork.1
bellwork.2
bellwork.3
Exit Ticket Answers. Always explain why!!!
exit.ticket.1
exit.ticket.2
exit.ticket.3
B.
Spiraled Skills
i. equation [assume uniform accelerations]
B1.
B2.
B3.
B4.
lFnetl = 600N
lFnetl = ?
W =?
W = 600N
m
= 80kg
m
= 12kg
m = 50kg
m = ?
a
=?
a
= 3m/s2
____
correct
B5.
____
correct
____
correct
B6.
N = 60N
B7.
B8.
N = 500N
bf = ?
D =?
bf = ?
μ = 0.4
____
correct
B9.
si = ?
k =
μ = 0.05
s
____
correct
D = 470N
20N/m/s
= 25m/s
k = 20N/m/s
a = 30ft/s2
= 1.85s
=?
____
correct
B11.
ṡ =?
d = 90m
d = 300m
t = ?
t = 3.25s
____
correct
s
____
correct
B10.
sf = 0
t
____
correct
a = 10m/s2
____
correct
____
correct
ii. time –speed charts
B12. A student fires a cannonball
vertically upwards with a speed of
30m/s. What is the cannonball’s
total flight time? The free-fall
acceleration is 10m/s2
B13. A student drops a baseball off the
top of a building. If the ball strikes
the ground 4s later, what was the
ball’s final speed? The free-fall
acceleration is 10m/s
s =0
B14. Make a time-speed chart for a
bicyclist, initially traveling 24mph
who slows to a stop in 6s.
STOP
si =
si =
sf =
a=
si =
t
sf =
a=
t
What is the cannonball’s
total flight time?
s
sf =
a=
s
t
What is the cannonball’s
speed after 4s?
What is the initial speed
of the ball?
s
What is the final speed of How long (in seconds)
the ball
does it take for the
bicyclist to stop?
What is bicyclists speed
after 3s?
C.
Free-Body Diagrams
C1. Bicyclist (pedaling)
C2. Bicyclist (coasting)
____
correct
C4. Physics Book
____
correct
C5. Projectile (neglect Drag)
The Seven Force Questions:
W: Is the object affected by gravity?
N: Is the object touching a surface?
T: Is a rope/string pulling the object?
D: Is the object moving?
bf: Is the object moving on a surface?
ff: Is a bike pedaling/car pressing gas?
Th: Is a rocket burning fuel/helicopter
blades spinning/fan on?
Force Directions
W: down, N: opposite surface, T: from
object along string, D: opposite motion,
bf: opposite motion, ff: forward,
Th: opposite air push
____
correct
C6. Skateboarder (neglect bf, D)
PHYSICS
FOR WOLVES
Replinger &
Barnhart
____
correct
C7. Load on the ground.
____
correct
C8. Hanging load.
____
correct
C9. Box (neglect bf, D)
load
counter weight
counter weight
load
counter weight
counter weight
chassis
chassis
____
correct
C10. Fan-Cart (the fan is on, neglect bf,
D)
____
correct
____
correct
C11. Fan-Cart (the fan is on, neglect bf,
D)
____
correct
____
correct
C12. Fan (on, blowing air upwards)
____
correct
D.
Free-Body Diagram Analysis
D1.
velocity direction:
Fnet =
speed is
D2.
velocity direction:
Fnet =
speed is
7N
D3.
velocity direction:
Fnet =
speed is
7N
7N
3N
2N
4N
2N
7N
7N
7N
____
correct
D4.
velocity direction:
Fnet =
speed is
____
correct
D5.
velocity direction:
Fnet =
speed is
3,000lb
120lb
____
correct
D6.
velocity direction:
Fnet =
speed is
?
120lb
200lb
50lb
?
120lb
170lb
50lb
3,000lb
3,000lb
velocity direction:
Fnet =
speed is
3,000lb
____
correct
D8.
velocity direction:
Fnet =
speed is
____
correct
D9.
velocity direction:
Fnet =
speed is
200lb
90lb
160lb
150lb
50lb
____
correct
D7.
3N
160lb
160lb
____
correct
____
correct
____
correct
D10. velocity direction:
Fnet =
speed is
D11. velocity direction:
Fnet =
speed is
130N
D12. velocity direction:
Fnet =
speed is
85N
U
S
A
U
S
A
U
S
A
40N
40N
60N
40N
60N
60N
____
correct
D13. velocity direction:
Fnet =
speed is
____
correct
D14. velocity direction:
Fnet =
speed is
____
correct
D15. velocity direction:
Fnet =
speed is
5N
U
S
A
?
70N
0.4N
200N
40N
500N
60N
5N
____
correct
D16. velocity direction:
Fnet =
speed is
____
correct
D17. velocity direction:
Fnet =
speed is
?
D18. velocity direction:
Fnet =
speed is
?
110N
70N
____
correct
80N
70N
40N
?
70N
40N
500N
60N
500N
____
correct
500N
____
correct
____
correct