Download presentation

Presentation is loading. Please wait.

Published bySelena Thomley Modified over 2 years ago

1
3.1 Spring Scales

2
Weight vs. Mass Springs Scales New ideas for today http://www.youtube.com/watch?v=MFXLhN3YNmg

3
Springs, torsion spring

4
Observations Lots of useful and fun things have springs in them Different types of materials act as springs Springs always seem to exert a force on you Scales measure your weight…sometimes How is all of this related?

5
A Free Spring A free spring adopts a certain length Its ends experience zero net force Its ends are in equilibrium The spring is at its equilibrium length

6
A Distorted Spring If you distort a spring, forces act on its ends These forces –act to restore the spring to equilibrium length –are called “restoring forces” –are proportional to the distortion Hooke’s Law

7
The restoring force on the end of a spring is equal to a spring constant times the distance the spring is distorted. That force is directed opposite the distortion. Restoring Force = – Spring constant x Distortion

8
F = -k x F = -k x = -k 0 = 0 F = -1 N/cm· 1 cm = -1 N F = -1 N/cm· 2 cm = -2 N F = -1 N/cm· (-1) cm = 1 N “+” Spring compression

9
Springs Always produce a force that opposes the distorting force <> Metal sheet

10
The figure shows a strobed photograph of a small ball being shot upward by a spring. The spring, with the ball on top of it, was initially compressed to P (its equilibrium position is Q). The ball left the spring at point Q and flew up to point R. Neglect air resistance. Which is a true statement? A.The spring force at P is less than the force of gravity on the ball. B.The spring force at P is greater than the force of gravity on the ball. C.The spring force at P is equal to the force of gravity on the ball. Clicker question

11
Follow the money work. What is the difference between the FLYBAR and a normal POGO stick? How do diving boards and trampolines allow you to jump higher? Why can you jump higher on the FLYBAR?

12
Spring Scales Use a spring to measure weight Scale

13
Equilibrium An object in equilibrium –experiences zero net force –is not accelerating At equilibrium, –individual forces balance one another perfectly –an object at rest remains at rest –an object in motion coasts

14
Clicker Question A scale sits on a skate. A mass hangs over a pulley on one end, and the other end is attached to a pole (fixed). Read the scale. Now, remove the fixed end and attach it to an identical mass hung over a pulley. Compared to the first case, does the scale read: A) Twice B) Half C) The same Scale on skates

15
Spring Scales and Acceleration Weight measurement requires equilibrium Without equilibrium, –spring force doesn’t balance weight –“measurement” is meaningless and inaccurate You must not bounce on a scale! (wait for the scale to settle before reading) Scale on spring

16
Clicker question: If her weight is 500 Newtons, what does the scale read (in Newtons)? A) 500 B) 1000 C) 550 D) 450 Mass= 50 kg

17
Total Weight = sum of all four measurements Two scales

18
A balance measures MASS Balance

19
The international mass standard is the only “old school” standard left There’s a big effort to redefine the kilogram: Watt balance Extremely round silicon sphere

Similar presentations

OK

1. What is a Force? A force is a push or pull on an object by another object and measured in newton (N). Forces are vectors 2 Force is a push Force.

1. What is a Force? A force is a push or pull on an object by another object and measured in newton (N). Forces are vectors 2 Force is a push Force.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on gulliver's travels part 1 Ppt on cloud computing download Ppt on different types of pollutions Home networking seminar ppt on 4g Ppt on network layer Ppt on smart card security Ppt on two point perspective examples Raster scan display ppt online 1st grade ppt on main idea Ppt on pre ignition knock