4*6 Forces Acting During Acceleration: Apparent Weight on a Roller Coaster WDYS??? (p406) . WDYT??? Your weight (does/does not) change when you are riding a roller coaster. 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 The weight of the mass is _____ N. 1 Acceleration (up, down, zero) Scale Reading Mass at rest Zero Mass up at constant speed Mass accelerating upward Up Mass at rest at top Mass down at constant speed Mass accelerating downward Down

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: 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. 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. 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 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 Normal Force (FN) = Apparent Weight (FN) = (m × g) + (m × a) 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!!! 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) When an object is moving up at constant speed, the 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) c) Apparent Weight = (m × g) – (m × a)