DAY 31
GOALS: SWBAT...
1. describe difference between mass & weight
2. Draw a basic FBD
3. Solve a variety of acceleration-related problems
WARM-UP: (These are questions to see what you know, so don't look up answers, just write what you think.)
1. What is a force?
2. What is the difference between mass and weight?
CLASSWORK:
1. CH 3 EXAM
2. Mass vs. Weight Notes
A. Watch the video, take notes, and answer the Edpuzzle Q's
B. Then read the notes below, and use them to answer the following:
- What is the difference between mass and weight?
- https://edpuzzle.com/media/57880ea9a163208e0e745ccf
Fill in the chart below
Base Dimensions: Mass Weight
SI (Metric) System
English (Standard) System
Mass is a measure of the amount of material in an object, being directly related to the number and type of atoms present in the object. It's the amount of "stuff" in an object. Mass does not change with a body's position, movement or alteration of its shape, unless material is added or removed.
An object with a mass of 1 kg on earth would have the same mass of 1 kg on the moon
Weight
Weight is the gravitational force acting on a body mass. The generic expression of Newton's Second Law (F=ma) can be transformed to express weight as a force by replacing the acceleration - a - with the acceleration of gravity - g - as
W = m g (2)
where
W = weight or gravitational force - F (N, lbf)
m = mass (kg, slugs)
g = acceleration of gravity on earth (9.81 m/s2, 32.17405 ft/s2)
HW:
Intro to Free-Body Diagrams (watch, take notes, answer Q's)
https://edpuzzle.com/media/57853ae627ed9aaf133db9f3
Pg 89: 1-3 solve. Show your work. You need to draw a picture for FBD's, ALWAYS...
GOALS: SWBAT...
- Define "Apparent Weight"
- Solve problems using FNET
- Prove to Mr. A that you have enough Geometry skillz to solve Physics problems
- Define "Resultant"
WARM-UP & HW CHECK (pg 100 #20; pg 101 #21, 23, 24, 26)
Your name is Marge, your mass is 50kg, and you are standing on a bathroom scale in an elevator. Starting from rest, the elevator accelerates downward at an acceleration of 2.00m/s2 for 2.00s, and then continues at a constant speed.
1. Is the scale reading during acceleration higher, lower, or the same as when the elevator is at rest?
2. Draw an FBD for the system (include the scale and Marge only). Define positive & negative
3. Find the force on the scale during the acceleration by using FNET
***If you get stuck, look at example problem #2 on pg 99***
CLASSWORK
1. Apparent Weight Notes
To determine the apparent weight, we need to consider Vertical Net Force and Acceleration
An object that accelerates vertically will always have to take into account the force of gravity. It is crucial in such problems to define a positive and a negative direction before finding your givens. After you choose positive and negative, draw your free body diagram and find your net force. Then solve the problem.
Video: https://www.youtube.com/watch?v=Cbp2Zh3RphU
2. Practice Problems
pg 100 #19, 22
SKIP. Check for Understanding
Newton's 1st law states that the acceleration of an object is equal to the sum of the forces acting on the object, divided by the mass of the object. What's wrong with this problem?
Put a prob using N 2nd law for them to solve.
Math Practice for Physics
- handout
- SOLUTIONS:
- Front
- Back
SKIP. Stump the Chump
Read page 100-101. On a 1/2 sheet of paper, come up with three fair reading quiz questions.
Staple all the 1/2 sheets together from your group. Turn them in.
HOMEWORK:
Due Tuesday: pg 113: 68, 69, 70, 71
Due Thursday: TBD