Physics Worksheet Lesson 10 Newton's Third Law of Motion
Transcription
Physics Worksheet Lesson 10 Newton's Third Law of Motion
Physics Worksheet 1 Newton’s Third Law of Motion – Action and Reaction Newton’s Law of Action and Reaction a) Newton’s third law: the law of action and reaction. 3 a) System: A systems is a coherent entity that has _________________. A system can be characterized and described by its __________________________________________ _________________ and the ___________ between __________________________________________ them. A system can be viewed as a collection of __________________________________________ ____________________ = ____________________ Name: System Concept __________________________________________ Newton’s third law formula: Section: ____________________________. b) Example: Identify the action and reaction (interaction) of a vase placing on the table: ____________________ = ____________________ b) Force is not something an object has, like mass. Force is an _____________ between two objects. To every action there is always a _________________. They are always: If action is always equal to reaction, why don’t they cancel each other out? (1) _______________________________________. __________________________________________ (2) _______________________________________. (3) _______________________________________. 2 c) d) Example: Why Does the Man-Box Move? i) Identify all the horizontal forces of in a ManBox diagram: Identifying Action and Reaction a) An easy way to identify action and reactions forces is to simply say: Action: Object A exerts a force on Object B. Reaction: ________________________________. ii) Identify all the horizontal forces of a Man system: b) Example: In the case of a falling boulder, Action: the Earth exerting a force on the boulder. Reaction: ___________________________________. c) Example: In the case of hanging a lamp from ceiling, iii) Identify all the horizontal forces of a Box system: Action: the ceiling exerting a force on the lamp. Reaction: ___________________________________. d) Example: In the case of hammering a nail, Action: the hammer exerting a force on the nail. iv) Identify all the horizontal forces of a Man-Box system Reaction: ___________________________________. Mr. Lin 1 Physics Worksheet e) Newton’s Third Law of Motion – Action and Reaction Identify all the horizontal forces of in a HorseCart diagram: ii) Identify all the horizontal forces of a Horse system: Name: h) Example: A 100 N pushing force at 30o angle is exerted on a 10 kg block against the wall. Identify and calculate all the forces acting on the block by drawing the free-body diagram Example: Why Does the Horse-Cart Move? i) Section: 4 Action and Reaction on Different Masses a) If action is equal to reaction, by applying Newton’s second law, we can write: ___________________ = _____________________ iii) Identify all the horizontal forces of a Cart system: According to Newton’s second law, acceleration is inversely proportional to the __________. So, the larger the mass, the ___________ the acceleration. iv) Identify all the horizontal forces of a HorseCart system b) Example: When considering a boulder falling to Earth, you can say Earth is also _________________________________________. Although the forces are equal, the masses are very unequal. Since Earths mass is so large, the f) Example: Why does a Rear-Wheel-Drive Car move? i) acceleration of the boulder is __________________. Identify all the horizontal forces of in a RearWheel-Drive Car diagram: c) Example: Based on the following diagram, calculate the acceleration of the girl. ii) Identify all the horizontal forces of a RearWheel-Drive Car system: 5 Interaction through a String a) Example: Based on the info from diagram, (a) find the readings of (b) and (c). g) Example: Why Does the Horse-Cart Move? i) Identify all the horizontal forces of in a FrontWheel-Drive Car diagram: ii) Identify all the horizontal forces of a FrontWheel-Drive Car system: Mr. Lin 2 Physics Worksheet Newton’s Third Law of Motion – Action and Reaction b) Example: Based on the info from diagram, find the readings on both scales. c) Name: Interaction with acceleration a) Weight in the Elevator: Analyze the weight changes in an elevator due to different accelerations. (i) at rest or constant speed (ii) accelerates upward (iii) accelerates downward (iv) accelerates downward at g (9.81 m/s2) Example: If the system is in equilibrium, based on the info from diagram, find (a) the tension forces FTA and FTC, and (b) the mass mC. d) Example: If the system is in equilibrium, based on the info from diagram, find (a) the tension forces T1, T2 and T3, and (b) the mass m. e) 6 Section: Example: If the system is in equilibrium, 𝜃 = 30! and m2 = 5 kg, based on the info from diagram, find (a) the tension forces T, and (b) the mass m1. Mr. Lin b) Example: An 800N person measures his weight in an elevator. If the elevator is accelerating upward at 2 m/s2, what will be reading on the scale? c) Example: A 10kg block is accelerated at 2 m/s2, as shown in the diagram. Find (a) the tension T of the rope, and (b) the mass m2. 3