Aptitude Test Problems in Physics Science for Everyone by S Krotov ( PDFDrive.com )

174 Aptitude Test Problems in Physics

and the white ball will simultaneously turn

through an angle 2st since the period of revolution

of the balls around their centre of mass coincides

with the period T. Therefore, the required dis-

tance is

L—1 1

3 1

4-(7t0+- 2 )

or for another arrangement of the balls (the white

and the green ball change places in the figure),

3 ' r 1 12

V 4+("73-7)

1.73. The centre of mass of the system consisting

of the blocks and the thread is acted upon in the

horizontal direction only by the force exerted by

the pulley. Obviously, the horizontal component

of this force, equal .to T (1 — cos cp), where T

is the_tension of the thread, is always directed to

Fig. 175

the right (Fig. 175). Since at the initial moment the
centre of mass is at rest above the pulley, during
motion it will be displaced along the horizontal to
the right. Hence it follows that the left block
reaches the pulley before the right block strikes the
table siace otherwise the centre of mass would be
to the left of the pulley at the moment of impact.
1.74. According to the initial conditions (the left
load is at rest, and the right load acquires the ve-
locity v), the left load will move in a straight line,
while the right load will oscillate in addition to the