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

144 Aptitude Test Problems in Physics

and obtain the following equation:

mg sin cc + ttmg cos a = ma 1.

The corresponding equation for the downward mo-

tion is

mg sin a — p.mg cos a = ma 2.

Let the distance traversed by the block in the

upward and downward motion be s. Then the time

of ascent t^1 and descent t 2 can be determined from

the equations

s (lag aati

2 2 '

By hypothesis, 2t 1 = t 2 , whence 4a 2 = al. Con-
sequently,

g sin a + pg cos a = 4 (g sin a — pg cos a),

and finally

p= 0.6 tan a.

1.44. If the lower ball is very light, it starts climb-

ing the support. We shall find its minimum mass

Fig. 152

ma for which it has not yet started climbing, but

has stopped pressing against the right inclined

plane. Since the support is weightless, the hori-

zontal components of the forces of pressure (equal

in magnitude to the normal reactions) exerted by

the balls on the support must be equal (Fig. 152);