A vector A has a magnitude of 48.0 m and points in a direction 20° below the positive x axis. A second vector, B, has a magnitude of 75 m and points in a direction 60.0° above the positive x axis?

Using the component method of vector addition, how do you find the magnitude and direction of the vector C=A +B?

2 Answers
Aug 5, 2016

The magnitude of C is 90.808 m, nearly, and the direction of C

makes 31.234^o, with the positive direction of the x-axis.

Explanation:

The vector

A=(x, y)=r(cos theta, sin theta) =48(cos (-20^o), sin (-20^o)) and,

likewise, the vector

B=75(cos 60^o, sin 60^o).

So, A=(45.105, -16.417) and B=(37,5, 64.952), nearly.

Now, the components of C=A+B are

(45.105, -16.417)+(37,5, 64.952)

=(45.105+37.5, -16.417+64.952)

=(82.605, 48.535)= r(cos theta, sin theta) =(x, y)

=96.808(cos 31.234^o, sin 31.234^o),

using r = sqrt(x^2+y^2), cos theta = x/r and sin theta = y/r .

The magnitude of C is 90.808 m, nearly, and the direction of C

makes 31.234^o, with the positive direction of the x-axis.

Aug 5, 2016

Magnitude of resultant vector is 95.81m and direction is 30.44^o above x-axis

Explanation:

As vector A has magnitude of 48.0m and points in a direction 20^o below positive x-axis (i.e. -20^o) and vector B has magnitude of 75.0m and points in a direction 60^o above positive x-axis.

Hence the angle between two vectors is 60-(-20)=80^o and hence

Magnitude of resultant vector is sqrt(48^2+75^2+2xx48xx75xxcos80^o

= sqrt(2304+5625+7200xx0.17365)

= sqrt(2304+5625+1250.28)=sqrt(9179.28)=95.81m

Direction wll be given by alpha=tan^(-1)((75sin80^o)/(48+75cos80^o))

= tan^(-1)((75xx0.9848)/(48+75xx0.17365))

= tan^(-1)((73.86)/(48+13.02375))=tan^(-1)(73.86/61.02375)

= tan^(-1)1.21035=50.44^o

But this is w.r.t. A and hence direction is 50.44^o-20^o=30.44^o above x-axis