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Physics on Friday 9-28-07. To do…Friday Answers for first test Questions on Homework handout Class example problem Hand in the graph created by you walking.

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Presentation on theme: "Physics on Friday 9-28-07. To do…Friday Answers for first test Questions on Homework handout Class example problem Hand in the graph created by you walking."— Presentation transcript:

1 Physics on Friday

2 To do…Friday Answers for first test Questions on Homework handout Class example problem Hand in the graph created by you walking before the motion detector with the analysis Talk about the causes of motion

3 To do Monday Hand in Handout #3 Hand in Graph work –Divide up, calculate velocity, calculate acceleration, determine overall velocity Forces- general information Forces –laws of motion Forces- free body diagram Homework #4 Test thursday

4 Any questions on the homework handout? Results are due on Monday, if needed

5 New homework 3 more question on Handout #4 Grade old homework and pass back tomorrow Test on Friday (primarily constant acceleration problems and review)

6 Do Now problem Joe runs with a constant velocity of 5.4 m/s for 20 s before he reaches a pile of leaves. It takes 1.5 s for Joe to come to a stop in the pile. What is his rate of acceleration in the leaf pile and how far did Joe travel overall?

7 Answer V f = V i + at 0 = a(1.5) = -3.6 m/s 2

8 What causes objects to move or change their motion?

9 Forces Contact (applied) Forces –Electromagnetic forces (most common) Non-contact Forces –Gravitational (most common) –Fields Anything that pushes or pulls is a force Units in Newtons (for this class)

10 Weight is a Force Force due to the pull of gravity Weight (W) = mass X acceleration due to gravity On earth, everything in free-fall accelerates at the same rate (9.8 m/s 2 ) towards Earth

11 Demonstration that all objects are pulled at the same rate Paper and book Paper-vs-paper The only reason why things do not fall at sam rate is air resistance

12 Determine your weight in Newtons Take you weight in lbs and divide by 2.2 The 1st action converts from lbs kg Kg is the common unit for Mass Mass is the amount of stuff that makes up an object

13 Mass is the measure of the inertia of an object Inertia = the amount resistance to change in motion The object that is the most massive, changes its velocity the least when a constant force is applied Golf, Magic Tricks

14 Difference between mass and weight Mass = measure of the amount of matter that makes up an object Weight is the amount of Force generated due to the pull of gravity

15 To find your weight in Newtons Weight = mass x = acceleration due to gravity on earth Change the location (moon, into space, on Jupiter): Change the acceleration value –Moon 1/6 th of earth = 1.67 –Jupiter about 2.5 times Earth = 25

16 What weighs 1000 N?

17 Football player (220 lbs)

18 What weighs 100 N?

19 Freshman backpacks

20 What weighs 10 N?

21 The average textbook

22 What weighs 1 N?

23 A smallish apple


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