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

Fig. 144

Solutions

135

vector BC equal to yector AB is the change in ve-

locity during the next time interval At. Therefore,

in the time interval 3At after the beginning bf

action of the force, the direction of velocity will

be represented by vector OD, and AB = BC =

Let the projections of vector AB on the x- and

y-axes be Av, and Aup. Then we obtain two equa-

tions:

(v Avx) 2 + Ay?, =

v 2

(v+ 2Avs)2+(2Avy)2= —

16 •

Since the final velocity satisfies the relation

2

Vf = (v ± 3AVO^2 (^3 AVy) 2 ,

using the previous equations, we obtain

vf = 4— v.

1.34. Since the motion occurs in the horizontal

plane, the vertical component of the force acting

on the load is mg, and the horizontal component is

given by F^2 — (mg) 2 = mgl/a 2 1, where a =

1.25 (Fig. 145). The horizontal acceleration of the