Download presentation

Presentation is loading. Please wait.

Published byOliver Morgan Modified over 2 years ago

1
Moments

2
Moment The moment of a force is a measure of the tendency of the force to rotate the body upon which it acts.

3
Terminology = F pivot distance = d lever arm The distance must be perpendicular to the force.

4
Moments Formula = F pivot Moment M M = d x F distance = d

5
Units for Moments ForceDistanceMoment English Customary Pound force (lbf) Foot (ft)lbf-ft SINewton (N)Meter (m)N-m

6
Rotation Direction In order to add moments, it is important to know if the direction is clockwise (CW) or counterclockwise (CCW). CCW is positive CW is negative

7
Right-Hand Rule Curl your fingers to match the direction of rotation. Thumb is pointing.... Up = Positive Down = Negative Toward You = Positive Away from You = Negative +

8
Right-Hand Rule THUMB POINTS TOWARD YOU POSITIVE

9
Right-Hand Rule THUMB POINTS AWAY FROM YOU NEGATIVE

10
Moment Calculations Wrench F = 20. lb d = 9.0 in. M = d x F Use the right-hand rule to determine positive and negative. d = 9.0 in. =.75 ft M = -(20. lb x.75 ft) M = -15 lb-ft (15 lb-ft clockwise) ¯

11
Moment Calculations Longer Wrench F = 20. lb d = 1.0 ft M = d x F M = -(20. lb x 1.0 ft) M = -20. lb-ft ¯

12
Moment Calculations L - Shaped Wrench F = 20. lb d = 3 in. =.25 ft M = d x F M = -(20. lb x.25 ft) M = -5 lb-ft ¯ 3 in. d = 1.0 ft

13
Moment Calculations Z - Shaped Wrench F = 20. lb d = 8 in. + 10 in. = 1.5 ft M = d x F M = -(20. lb x 1.5 ft) M = -30. lb-ft ¯ 8 in. 9 in. 10. in.

14
d = r = 50. cm = 0.50 m M = d x F Use the right-hand rule to determine positive and negative. M = 100 N x 0.50 m M = 50 N-m Moment Calculations Wheel and Axle F = 100 N r = 50. cm +

15
50. o F y = Fsin50.° = (100. N)(.766) F y = 76.6N d = r = 50. cm = 0.50 m M = d x F y M = 76.6 N x 0.50 m M = 38 N-m Moment Calculations Wheel and Axle F = 100. N r = 50. cm FyFy

16
What is Equilibrium? The state of a body or physical system with an unchanging rotational motion. Two cases for that condition: 1.Object is not rotating OR 2.Object is spinning at a constant speed In either case rotation forces are balanced: The sum of all moments about any point or axis is zero. ΣM = 0 M 1 + M 2 + M 3... = 0

17
Moment Calculations See-Saw

18
ΣM = 0 M 1 + M 2 = 0 Use the right-hand rule to determine positive and negative. M 1 = -M 2 d 1 x F 1 = d 2 x F 2 25lb x 4.0ft - 40. lb x d 2 =0 100 lb-ft = 40. lb x d 2 Moment Calculations See-Saw F 1 = 25 lb F 2 = 40. lb d 1 = 4.0 ft d 2 = ? ft 40. lb 40. lb 2.5 ft = d 2 + ¯

19
ΣM = 0 M B + M C = 0 M B = -M C d AB x R By = d AC x F C 10.00 ft x R By = 3.00 ft x 35.0 lb 10.0 ft x R By = 105 lb-ft Moment Calculations Loaded Beam d AB = 10.00 ft d AC = 3.00 ft A C B R Ay F C = 35.0 lb R By 10.00 ft 10.00 ft R By = 10.5 lb R Ay + R By = 35.0 lb R Ay = 35.0 lb – 10.5 lb = 24.5 lb Select A as the pivot location. Solve for R By

20
A B C D F c = 600. lb Moment Calculations Truss 24 ft 8 ft 12 ft F B = 500. lb Replace the pinned and roller supports with reaction forces. R Ay R Ax R Dy d AC = 24 ft d CD = 8 ft d CB = 12 ft d AD = 32 ft

21
A B C D F c = 600. lb Moment Calculations Truss d AC = 24 ft d CD = 8 ft d CB = 12 ft d AD = 32 ft 24 ft 8 ft 12 ft F B = 500. lb R Ay R Ax R Dy Select A as the axis of rotation. Solve for R DY 12 ft ΣM = 0 M D – M B – M C = 0 M D = M B + M C d AD x R Dy = (d CB x F B ) + (d AC x F C ) 32 ft x R Dy = (12 ft x 500. lb) + (24 ft x 600. lb) R Dy x 32 ft = 6000 lb-ft + 14400 lb-ft R Dy x 32 ft = 20400 lb-ft 32 ft 32 ft R DY = 640 lb

Similar presentations

OK

SHEAR AND BENDING MOMENT DIAGRAMS IN HORIZONTAL BEAMS WITH

SHEAR AND BENDING MOMENT DIAGRAMS IN HORIZONTAL BEAMS WITH

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on bluetooth based smart sensor networks inc Ppt on service oriented architecture ppt Ppt on food chains and webs Ppt on revolution of the earth and seasons diagram Ppt on area of plane figures worksheets Ppt on next generation 2-stroke engine pistons Ppt on home security systems Ppt on low level languages Ppt on enzymes Ppt on object-oriented programming encapsulation