Engineering Mechanics - Force Vectors - Discussion

Discussion :: Force Vectors - General Questions (Q.No.4)

4. 

Determine the magnitude and direction of the resultant force.

[A]. R = 80.3 lb, = 106.2° CCW
[B]. R = 80.3 lb, = 73.8° CCW
[C]. R = 72.1 lb, = 63.6° CCW
[D]. R = 72.1 lb, = 116.4° CCW

Answer: Option A

Explanation:

No answer description available for this question.

Sajun said: (Jan 10, 2012)  
Its simple.

By adding the why components and x components vectoricaly we are able to get the answer.

Dan said: (Jan 22, 2012)  
Are you sure A is the right answer? you might want to find the tangent again.

Sathish Uthayasuriyan said: (Apr 10, 2012)  
If we take tangent of these two the answer will be Option B.

Snehasish said: (Jun 19, 2012)  
CCW means angle makes from west corner (-ve X-axis) i.e. 180 - 73.77 = 106.228 ~ 106.2.

Cj Manglalan said: (Jul 22, 2012)  
CCW I THINK IT MEANS IT ROTATES Counter ClockkWise

FOR F:

F1x= (60 lb) (cos 45)= 42.426
f1y= 42.426 (sin 45=cos45) or (60 lb)(sin 45)
FOR P:

p1x= (40lb)(sin 30) = 20
p1y= (40lb)(cos 30) =34.641

sumamtion of forces along x =42.426 + 20 = -22.426
summation of forces along y =42.426 + 34.641 = 77.067

for R:

R= square root of (((-22.426)square)+ ((77.067)square))

for angle:

=arc tangent (y/x)
=arc tangent (77.067/-22.426) = -73.8

since the angle is negative you will subtract it to 180

the angle is

180-73.8 = 106.2

D.Mani Obul Reddy said: (Apr 15, 2014)  
Horizontal components = 60cos45 - 40sin30 = 22.426.
Vertical components = 60sin45+40cos30 = 77.067.

R = SQUARE ROOT(22.426)^2+(77.067)^2 = 80.26.
ANGLE = TAN inverse of(77.067/22.426) = 73.77.

180 - 73.77 = 106.2 ccw.

Ng Kl said: (Sep 29, 2014)  
I calculated the answer is -7.78.

(60 lb) (cos 45) is negative.

Bob said: (Sep 26, 2015)  
Why do you have to minus 73.7 from 180?

Krishna said: (Sep 2, 2016)  
@Mani Obul.

Yes, why you subtracted 73.7 from 180?

Sarvjeet Singh said: (Nov 5, 2016)  
R = 80.25 s/ direction = 73.72.

Thato said: (Mar 17, 2017)  
@All.

Try parallelogram method to get the answer.

Toms said: (Aug 10, 2017)  
How would you solve the x and y components if you don't know the angles?

Bright said: (Oct 14, 2017)  
Why is 60cos45 negative?

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