An iron pillar consists of a cylindrical portion of 2.8m height and 20cm. in diameter and a cone of 45 cm height surmounting it find the weight of the piller 1cm3 of iron weight 7.5g
The volume of the iron pillar=Volume of the cylindrical part+Volume of cone
V=Vcyl+Vcon
∴V=πr2hcyl+13πr2hcon
Now, r=d2=202=10cm
hcyl=2.8m=280cm
hcon=45cm
∴V=π(10)2×280+13π(10)2×45
V=π(100×280+100×15)
V=π(100×(280+15))
V=π(100×295)=π×=29500cm3
Thus Weight=V×weight per cm^3
w=29500×7.5=221250g=221.25kg