Download 4*6 Forces Acting During Acceleration: Apparent Weight on a Roller

4*6 Forces Acting During Acceleration:
Apparent Weight on a Roller Coaster
 WDYS??? (p406)
1. .
2. .
3. .
 WDYT???
1. Your weight (does/does not) change when you are
riding a roller coaster.
2. If you were sitting on a scale, it (would/would not)
give different readings at different places on the roller
coaster.
4*6 Investigate (p407-410)
You will investigate the apparent weight changes you feel
when you are on a roller coaster by using a spring scale
and bathroom scale.
Part A: Moving the Mass at a Constant Speed
1. The weight of the mass is _____ N.
2. 1
Acceleration
Scale
(up, down, zero)
Mass at rest
Zero
Mass up at constant speed
Zero
Mass accelerating upward
Up
Mass at rest at top
Zero
Mass down at constant speed
Zero
Mass accelerating downward
Down
Reading
4*6 Investigate (p407-410)
2b) When moving up at a constant speed, the scale
reading is _____N.
3a) When moving down at a constant speed, the scale
reading is _____N.
4. Newton’s 1st Law = Inertia
Newton’s 2nd Law Fnet = m × a
Constant Speed = Zero Acceleration
If there is no acceleration, then the Fnet = zero
4*6 Investigate (p407-410)
4a) When it is at rest, the Fweight must equal Fspring
Draw a free-body diagram:
4*6 Investigate (p407-410)
5. The arrows you draw to represent forces are _____.
5a) Fweight is drawn ____ because Earth is pulling the
mass )_____.
5b) Fspring is drawn _____ because the spring is
applying a force _____ on the mass.
5c) There are no other forces acting on the box!!!
5d) The Fweight and Fspring (are/are not) equal in length.
4*6 Investigate (p407-410)
Part B:
Accelerating the Mass
1a) When the mass accelerates up, the scale reads___N.
1b) Newton’s 2nd Law (F = m × a) shows us that if
there is an acceleration then there must be a _____,
therefore the scale reading is _____.
1c) Draw a free-body diagram:
4*6 Investigate (p407-410)
2a) The Fweight is _____ because Earth pulls the object
_____.
2b) The spring pulls the mass _____.
2c) There are no other forces acting on the box!!!
2d) The Fweight is _____ than the Fspring because there is
a net force acting _____ due to the fact the
acceleration is moving up.
4*6 Investigate (p407-410)
4. When the mass is accelerating upward, the spring
scale displays a larger value than the mass’s weight in
order to provide a Fnet that moves you.
5. When the mass stops moving upward, the scale will
read _____ than the original weight because the mass
requires a downward acceleration.
4*6 Investigate (p407-410)
6a) When the mass accelerates down, the scale reads
_____N.
6b) Draw a free-body diagram:
4*6 Investigate (p407-410)
 CONCLUSION:
1. When a mass has NO net force acting on it the weight
appears to be (the same as/more than/ less than) it
should be.
2. When a mass has a POSITVE net force acting on it the
weight appears to be (the same as/more than/ less than)
it should be.
3. When a mass has a NEGATIVE net force acting on it the
weight appears to be (the same as/more than/ less than)
it should be.
4*6 Physics Talk: (p410-415)
Forces Acting During Acceleration
1. Using Newton’s 1st and 2nd Law to Explain Forces
Acting During Constant Speed and Acceleration
 Newton’s 1st Law = Inertia
 Newton’s 2nd Law  a = F/m
F = m×a
m = F/a
 Zero acceleration = constant velocity = NO Fnet
 Balanced = NO movement
 Unbalanced = movement where the vector is longer
and the magnitude (#N) is larger
4*6 Physics Talk: (p410-415)
Forces Acting During Acceleration
Constant Speed UP =
Constant Speed DOWN =
SAME scale reading =
Fweight = Fspring
4*6 Physics Talk: (p410-415)
Forces Acting During Acceleration
Acceleration UP =
LARGER scale reading =
Fspring is GREATER than Fweight
Acceleration DOWN =
SMALLER scale reading =
Fspring is LESS than Fweight
4*6 Physics Talk: (p412-413)
Forces Acting During Acceleration
2. Calculating Acceleration
 Force =
m × a, its units are Newtons (N)
 Weight = m × g, its units are Newtons (N)
 Therefore, Force = Weight
 Free Fall (broken elevator cable)  the scale
would NOT push up at all and the reading
would be ZERO
4*6 Physics Talk: (p414)
Forces Acting During Acceleration
3. Apparent Weight
Acceleration UP =
MORE Contact Force =
LARGER “Apparent” Weight =
You feel like you weigh MORE!!!
Acceleration DOWN =
LESS Contact Force =
SMALLER “Apparent” Weight =
You feel like you weigh LESS!!!
Normal Force (FN) = Apparent Weight
(FN) = (m × g) + (m × a)
Apparent Weight = (m × g)+ (m × a)
Physics Talk: (p415)
Forces Acting During Acceleration
4. Air Resistance
 Free Fall  the ONLY force acting on an
object is GRAVITY; (Fweight)
 Acceleration due to GRAVITY is IDENTICAL
for ALL objects falling on Earth…10m/s/s!!!!!
 Air Resistance  the force working AGAINST
GRAVITY that pushes upward on falling
objects; (Fspring)
4*6 Checking Up (p415)
1. When an object is moving up at constant speed, the
2.
3.
4.
5.
sum of all the forces acting on an object = _____.
When accelerating upward, the reading on the
bathroom scale is _____ than the person’s weight.
You feel like you weigh more when accelerating
upward because you have _____ contact force.
When falling with the elevator, you are accelerating
downward at _____. To fall at this rate, the ONLY
force acting on you is the force of your weight, so the
reading on the bathroom scale is _____.
__________ slows down a falling raindrop.
4*6 Physics To Go (p418)
1a) v = a×t =
b) v = a×t =
c) v = a×t =
2a) v = a×t =
b) v = a×t =
c) v = a×t =
3a) The block (is/is not) at rest.
b) The block (is/is not) moving up at a constant speed.
c) The block (is/is not) accelerating down.
5. Real Weight = 140
Apparent Weight = 137
The elevator is accelerating (up/down).
4*6 Physics To Go (p418)
6. If the real weight = 600N and going from 2nd to 5th
floor then the acceleration is _____, will feel _____, and
the scale will read _____.
7a)As the elevator moves downward, the acceleration is
_____ and the scale reading is _____.
b) Apparent Weight = (m × g) – (m × a)
8a) Apparent Weight = (m × g) – (m × a)
b) Apparent Weight = (m × g) – (m × a)
c) Apparent Weight = (m × g) – (m × a)