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suppose the position vector was r= d e_r , where theta is fixed (i.e., e_r does not rotate) but the length d is not constant. which one of the following is correct?

a. Velocity = d theta (theta-dot)
b. Velocity is zero
c. Velocity is (d-dot) theta e_theta
d. Velocity is (d-dot) er >



Answer :

The velocity as calculated is Option d) Velocity is (d-dot) er

As given in the question the position vector is

r = d e_r

The length d is not constant with time but varies with it

The theta is fixed hat is e_r does not rotate that is it is constant with time.

To find the velocity we use the formula

velocity v = [tex]\frac{dr}{dt}[/tex]       where r is the position vector

⇒ v = [tex]\frac{d(de_r)}{dt}[/tex]

⇒v = (d-dot)e_r + d( e_r - dot)         (where dot means the time derivative)

⇒v= (d-dot) er                    (e_r - dot =0 because e_r is fixed )

∴The value of velocity = (d-dot) er which is

Learn more about the velocity formula:

brainly.com/question/19979064

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