Due 12/1 Ap Physics Week 14 Homework Rubric Page 132-141

DUE 12/1 AP PHYSICS WEEK 14 HOMEWORK RUBRIC PAGE 132-141

AREA-FORCES POSSIBLE POINTS CORNEL NOTE FORMAT: Heading, Page Set Up, Legible, Organized, Color 5 What is force and how does it relate to Newtons 15 - One newton (N) is about the weight of a cellphone—a rather small force. You can easily exert a force of 100 N or more with one arm. Technically, one newton is the force required to change an object’s velocity by one meter per second in one second. This is where the newton gets its fundamental units: One newton is the force required to accelerate one kilogram at one meter per second per second (1 N = 1 kg m/s2). Compare Newton’s, Pounds, and Kilograms and how to convert them from one to the other 15

In your everyday life, force is often measured in pounds. One pound (lb) is equal to 4.448 N. If you weigh 100 lb you also weigh 444.8 N. In the grocery store, pounds are divided into ounces. One pound equals 16 ounces, so one newton is a just a bit less than 4 ounces weight?Weight is a force that results from the action of gravity on mass.

If a person has a weight of 125 lb, then what is that person’s mass in kilograms?

Asked: mass

Given: weight Fw = 125 lb

equation for weight: Fw = mg Relationships: conversion factor: (444.8 N)/(1 lb) = 1 acceleration due to gravity: g = 9.8 N/kg Convert weight from pounds to newtons: 125 lb=(125 lb)(4.448 N1 lb)=556 N Calculate mass using weight equation: Solution: Fw=mg⇒m=Fwg=556 N9.8 N/kg=56.7 kg

Summarize the process of creating a Free body diagram incorporating Normal Force 15

How do I draw a free-body diagram? A free-body diagram needs to be neither exact nor artistic! A good free-body diagram is just an outline of the object that shows the approximate locations and assumed directions and names of the forces acting on each single object. The above-right diagram contains two balls, and each one gets its own free-body diagram. Equally important is that each unique force must have a unique name. In the example we use subscripts to name the four different forces F1, F2, F3, and F4. Read the text aloud Show Two terms of F₃ Which forces to include A tricky aspect of drawing free-body diagrams is to identify all the forces that act and to include only those forces that act on the object. The phrase “on the object” is important because there may be forces that come from the object but act on something else. Read the text aloud

Discuss the term Center of mass, how it is found, and why it is needed for a free body diagram. 15 The center of mass is the average location of all the mass contained in the object. When constructing a free-body diagram, the weight force is drawn downward from the center of mass. Draw the free body diagrams on page 139, explain how the net force is calculated 15

The direction of a force matters when determining the net force. Force, like position, is a vector. In one-dimensional problems positive and negative signs are used to indicate direction. Forces should be assigned positive and negative values that correspond to direction.

When solving problems involving forces and free-body diagrams, you must choose which direction is positive. The opposite direction then becomes negative. Diagrams are often chosen such that right and up is positive and left or down is negative. The choice, however, is arbitrary and it may be easier for some problems to choose differently. Once you choose the positive direction, you must be consistent throughout the entire solution process. Read the text aloud When can forces not be added? In most physics problems you will need to consider the net force separately in each of the perpendicular directions. For example, a 200 N upward force cannot cancel with a −200 N force to the left because these forces do not act along the same line. The net force may be different in different directions. In the example above, the vertical net force is zero but the net force in the horizontal direction may not be zero. Read the text aloud Complete all parts of question 5 on page 141 25

a. The woman and the stool are both in equilibrium. Neither is moving. An object at rest is in equilibrium. b. The woman is subject to a zero net force; so is the stool. Since the woman and the stool are both in equilibrium, each must experience zero net force. The forces acting upon each of them must all cancel each other out. c. Draw an outline of the woman. Next, draw a downward arrow that starts at her center of mass. (This arrow represents her weight, which is a force.) Finally, draw an upward arrow below the woman, one that points toward her body. This arrow represents the normal force on the woman from the stool. d. The net force on the woman must be zero, since she is in equilibrium. The normal force must therefore be just as strong as her weight (120 lb, or roughly 530 N).

TOTAL 105