PHYSICS SH WD WN
Student 1:
Student 2:
Student 3:
chooses a
showdown
question at
random from
the envelope
and hands it
to Student 2.
reads the
question to
Student 3.
She also
silently reads
the answer.
answers the
question.
Student 2
confirms the
answer.
Students
4 & 5:
assist
Student 3
as needed.
NWODWOHS
TEAMS ROTATE JOBS AFTER EACH QUESTION
SH WD WN PROCEDURE:
1.
2.
3.
Draw the FBD
Write and/or solve
the necessary
equations.
Solve
Fnet = ???
F = ma
Find the force that produces an acceleration of 4.0 m/s/s for a 0.50 kg cantaloupe.
Find the force that produces an acceleration of 4.0 m/s/s for a 0.50 kg cantaloupe.
m
F = ma = (0.50 kg)(4.0 /s2) = 2N
A force of 44.0 N is applied to a 2.0 kg discus. What is the acceleration of the discus? A force of 44.0 N is applied to a 2.0 kg discus. What is the acceleration of the discus? F = ma
∴
a = F m
a = (44.0 N) = 22m/s2
(2.0 kg)
A Porsche 911 accelerates to 27 m/s (60 mph) due North in 3.0 s. What is the acceleration of the car? And if the car has a mass of 1400 kg, what is the average net force acting on the Porsche? A Porsche 911 accelerates to 27 m/s (60 mph) due North in 3.0 s. What is the acceleration of the car? And if the car has a mass of 1400 kg, what is the average net force acting on the Porsche? m
/s
27 v
Δ
= = 9m/s2
a = 3.0 s
Δt
m
Fnet = ma = (1400 kg)(9 /s2) Fnet = 12600N Glenbard West’s quarterback is pushed back by the opposing front line with a force of 400 N. One of his own teammates pushes him forward with a force of 640 N. Assume the quarterback adds no force of his own, and has a mass of 120 kg. What is his acceleration? PHYSIC
S
Glenbard West’s quarterback is pushed back by the opposing front line with a force of 400 N. One of his own teammates pushes him forward with a force of 640 N. Assume the quarterback adds no force of his own, and has a mass of 120 kg. What is his acceleration? Fnet = 640 N ­ 400 N = 240 N
∴
S
FNET = ma
PHYSIC
400 N
640 N
(240 N)
m
F = = 2
/s2
a = m (120 kg)
What is the weight of a 100 kg person? What is the weight of a 100 kg person? m
F = ma = (100 kg)(9.8 /s2) = 980 N
If a person has a mass of 50 kg, they have a weight of about 500 Newtons on Earth. On Mars, the acceleration of gravity is about 3.7 m/s/s. What is this person’s weight on Mars? If a person has a mass of 50 kg, they have a weight of about 500 Newtons on Earth. On Mars, the acceleration of gravity is about 3.7 m/s/s. What is this person’s weight on Mars? F = ma m
F = (50 kg)(3.7 /s2) F = 185 N
If a person has a mass of 50 kg, they have a weight of about 500 Newtons on Earth. On Jupiter, the acceleration of gravity is about 22.9 m/s/s. What is this person’s weight on Jupiter?
If a person has a mass of 50 kg, they have a weight of about 500 Newtons on Earth. On Jupiter, the acceleration of gravity is about 22.9 m/s/s. What is this person’s weight on Jupiter?
F = ma F = (50 kg)(22.9m/s2) F = 1145 N
A single fig newton cookie has a mass of 0.0143 kg. How many fig newtons does it take to have a weight of 1 Newton?
mmm...
fruit &
cake
A single fig newton cookie has a mass of 0.0143 kg. How many fig newtons does it take to have a weight of 1 Newton?
m
F1 = ma = (0.0143 kg)(9.8 /s2) F1 = 0.14 N
!
m
No
No
m
!
!
Nom
1 N ≈ 7
0.14 N
If you push a 50 kg desk across the floor with 60 N of force, and there is a frictional force of 20 N, what is the acceleration of the desk? If you push a 50 kg desk across the floor with 60 N of force, and there is a frictional force of 20 N, what is the acceleration of the desk? Fnet = 60 N ­ 20 N = 40 N
20 N
60 N
FNET = ma
∴
(40 N)
m
F = /s 2
= 0.8
a = (50 kg)
m
What is required to change an object’s velocity? What is required to change an object’s velocity? FORCE
Which is heavier, 1000 kg of rocks, or 1000 kg of feathers?
Which is heavier, 1000 kg of rocks, or 1000 kg of feathers?
Since they have the same MASS, they also have the same WEIGHT!!!
10,000 N
10,000 N
If a truck has a certain acceleration with a full load, estimate the truck’s acceleration empty (assuming it’s now half the weight).
If a truck has a certain acceleration with a full load, estimate the truck’s acceleration empty (assuming it’s now half the weight).
Fengine = ma
Fg = mg
DOUBLE ACCELERATION!!!
Fengine = (1/2m)(2a)
1
1
/2Fg = ( /2m)g
If the same force is applied to two objects of different masses, what can you say about their accelerations?
If the same force is applied to two objects of different masses, what can you say about their accelerations?
For Constant F:
If m ,
a
If m ,
a
INVERSELY
PROPOERTIONAL
SHO
WDO
W
N
THE SHOW (DOWN) IS OVER!