Question

Multiple Choice:    Place the letter of the best response in the space provided. Ignore air friction unless otherwise instructed. Assume g = 9.81 m/s² and G = 6.6673 x 10^-11 N∙m²/kg². Explain the answer pls legible.

_____ 2.      Some CD-ROM drives can spin your CD at 4000 rpm. The period of each revolution in this motion would be closest to

           A.       1.5 ms                      B.       15 ms            C.            0.25 ms                   D.       2.5 ms

_____3.          An object is in uniform circular motion at a radius of 10.0 m. The period of the motion is 3.0 s. If a second object is in uniform circular motion with a radius of 5.0 and the same period as the first object, its centripetal acceleration will be

          A.          double the acceleration of the first object

          B.          one-half the acceleration of the first object

          C.          four times the acceleration of the first object

          D.          one-fourth the acceleration of the first object

_____ 4.         An object that is in uniform circular motion has its speed double while its radius is held constant. What effect does this have on the centripetal acceleration?

          A.          it will double        B.       it will increase by about 40%

          C.          it will quadruple   D.      it will decreased by about 40%

_____ 7.       A net centripetal force of 120 N is used to keep a 0.50 kg object in uniform circular motion at a radius of 80 cm. The speed of the object would be nearest to   

           A. 13.8 m/s            B.       138 m/s                    C.           19.2 m/s                   D.       192 m/s

Answer 1

here,

2)

angular speed , w = 4000 rpm = 418.67 rad/s

the time period , T = 2 *pi/w

T = 2*pi/418.67 s = 0.015 s = 15 ms

3)

the cnetripital accelration , a = w^2 * r

as the radius of circle is halved

and same time period

then they have same angular speed

so, the centripital accelration is also halved

the correct option is B)

4)

the centripital accelration , ac = v^2 /r

when radius is constant

and speed is doubled

the new accelration is four times

so, correct option is C)

7)

let the speed of the object be v

the centripital force , Fc = m * v^2 /r

120 = 0.5 * v^2 /0.8

solving for v

v = 13.8 m/s

the correct option is A) 13.8 m/s