PhysicsLAB: Action-Reaction #2

PhysicsLAB

CP Workbook
Action-Reaction #2

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Refer to the following information for the next thirteen questions.

Nellie Newton holds an apple weighing one newton at rest on the palm of her hand. The force vectors shown are the forces that act on the apple.

To say the weight of the apple is 1 N is to say that a downward gravitational force of 1 N is exerted on the apple by

the earthher hand

Nellie's hand supports the apple with normal force N, which acts in a direction opposite to W. We can say N

equals Whas the same magnitude as W

Since the apple is at rest, the net force on the apple is

zerononzero

N is equal and opposite to W. We ____ say that N and W comprise an action-reaction pair.

cancannot

The reason is because action and reaction always

act on the same objectact on different objects

and here we see N and W

both acting on the appleacting on different objects

In accord with the rule, "If ACTION is A acting on B, then REACTION is B acting on A," if we say action is the earth pulling down on the apple, reaction is

the apple pulling upon the earth
Nellie's hand pushing up on the apple

To repeat for emphasis, we see that N and W are equal and opposite to each other

and comprise an action-reaction pair
but do not comprise an action-reaction pair

Another pair of forces is N [shown] and the downward force of the apple against Nellie's hand [not shown]. This force pair ____ an action-reaction pair.

isis not

Suppose Nellie now pushes upward on the apple with a force of 2 N. The apple

is still in equilibriumaccelerates upward

and compared to W, the magnitude of N is

the same
twice
not the same, and not twice

Once the apple leaves Nellie's hand, N is

zerostill twice the magnitude of W

and the net force on the apple is

zeroonly Wstill W - N, a negative force

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Resource Lesson:	RL - Advanced Gravitational Forces RL - Air Resistance RL - Air Resistance: Terminal Velocity RL - Forces Acting at an Angle RL - Freebody Diagrams RL - Gravitational Energy Wells RL - Inclined Planes RL - Inertial vs Gravitational Mass RL - Newton's Laws of Motion RL - Non-constant Resistance Forces RL - Properties of Friction RL - Springs and Blocks RL - Springs: Hooke's Law RL - Static Equilibrium RL - Systems of Bodies RL - Tension Cases: Four Special Situations RL - The Law of Universal Gravitation RL - Universal Gravitation and Satellites RL - Universal Gravitation and Weight RL - What is Mass? RL - Work and Energy
Worksheet:	APP - Big Fist APP - Family Reunion APP - The Antelope APP - The Box Seat APP - The Jogger CP - Action-Reaction #1 CP - Equilibrium on an Inclined Plane CP - Falling and Air Resistance CP - Force and Acceleration CP - Force and Weight CP - Force Vectors and the Parallelogram Rule CP - Freebody Diagrams CP - Gravitational Interactions CP - Incline Places: Force Vector Resultants CP - Incline Planes - Force Vector Components CP - Inertia CP - Mobiles: Rotational Equilibrium CP - Net Force CP - Newton's Law of Motion: Friction CP - Static Equilibrium CP - Tensions and Equilibrium NT - Acceleration NT - Air Resistance #1 NT - An Apple on a Table NT - Apex #1 NT - Apex #2 NT - Falling Rock NT - Falling Spheres NT - Friction NT - Frictionless Pulley NT - Gravitation #1 NT - Head-on Collisions #1 NT - Head-on Collisions #2 NT - Ice Boat NT - Rotating Disk NT - Sailboats #1 NT - Sailboats #2 NT - Scale Reading NT - Settling NT - Skidding Distances NT - Spiral Tube NT - Tensile Strength NT - Terminal Velocity NT - Tug of War #1 NT - Tug of War #2 NT - Two-block Systems WS - Advanced Properties of Freely Falling Bodies #1 WS - Advanced Properties of Freely Falling Bodies #2 WS - Calculating Force Components WS - Charged Projectiles in Uniform Electric Fields WS - Combining Kinematics and Dynamics WS - Distinguishing 2nd and 3rd Law Forces WS - Force vs Displacement Graphs WS - Freebody Diagrams #1 WS - Freebody Diagrams #2 WS - Freebody Diagrams #3 WS - Freebody Diagrams #4 WS - Introduction to Springs WS - Kinematics Along With Work/Energy WS - Lab Discussion: Gravitational Field Strength and the Acceleration Due to Gravity WS - Lab Discussion: Inertial and Gravitational Mass WS - net F = ma WS - Practice: Vertical Circular Motion WS - Ropes and Pulleys in Static Equilibrium WS - Standard Model: Particles and Forces WS - Static Springs: The Basics WS - Vocabulary for Newton's Laws WS - Work and Energy Practice: Forces at Angles TB - Systems of Bodies (including pulleys) TB - Work, Power, Kinetic Energy

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