Bukhovtsev-et-al-Problems-in-Elementary-Physics

MECHANICS 31
Fig. 44 Fig. 45
a
r
~~~-,A
I
I
rl
I
C :
- ..-----10
I
I
I
rl
II
Fig. 46 Fi,. ,g
~~~";'6
t 16. Determine the centre of gravity of a homogeneous thin
semicircle with a radius r,
t 17. Determine the centre of gravity of a thin homogeneous
wire bent over an arc with a radius r (Fig. 45).
t 18. Determine the centre of gravity of a thin homogeneous
plate cut in the form of a sector with a radius r and a central
angle a (Fig. 46).
119. Determine the centre of gravity of a thin homogeneous
plate having the form of a rectangle with sides' and 2r which
a semicircle with a radius, is cut out of (Fig. 47).
1-6, Work and Energy
120. What work will be performed if a force of 3 kgf is used
to lift a load of 1 kgf to a height of 5 metres?
121. In the formula for work W=kFs, the coefficient k=l
if all the quantities are given in the same system of units.
What is the coefficient k if the work is measured in joules, the
force in kgf and the distance in centimetres?