Physics ( Pressure )

dbowie SG

Three cylindrical blocks X,Y,Z are made of different densities 2.00g/cm^3, 5.00g/cm^3 and 10.00g/cm^3. If the sides of each block resting on a level surface has an area of 2cm^2, 4cm^2 and 6cm^2 and the height of block X is 10cm, calculate the

( i ) weight of block X,

( ii ) pressure exerted by block X on the surface,

( iii ) heights of block Y and Z if pressure exerted by each block on the surface is the same.

( Take g=10m/s^2 )

unclebutcher SG

i.) Weight X: (10cm)(2cm^2)*(2.00gcm^-3)*(10Nkg^-1)/1000(to convert G to KG)=0.4N

ii.) P=F/A

P= Weight/base area
= (0.4N)/(2/(100^2)m^2)
= 4000Pa

iii.) P=F/A
F=mg
P=mg/A
m=(base area)(height)
Thus
P=(base area)(height)(g)/A

for Y

P= (4)(height)(10)/4

for Z

P= (6)(height)(10)/6

cross multiply.

im not sure if im right cuz im doing it mentally without pen and paper,and im really shagged now.sorry if answer is wrong. eagle help check? i think iii.) is wrong

starmoonsun SG

huh i dun understand part 2.

eagle SG

part 2 he's converting the 2cm^2 into m^2 because when we use the equations, we need to bear in mind to convert everything to SI Units

eagle SG

(i) Unclebutcher is correct

(ii) Unclebutcher's workings correct, but careless
area of block X = 2 cm^2 = 2/10000 m^2
Hence, pressure = 0.4 / (2/10000) = 2000Pa

(iii)
Block Y:
Weight = 2000Pa * (4/10000) = 0.8N = 80g
Hence, 5 * 4 * h = 80
h = 4 cm

Block Z:
Weight = 2000Pa * (6/10000) = 1.2N = 120g
Hence, 10 * 6 * h = 120
h = 2 cm

There's a slightly shorter way to do because they are cylinders, but it will be damn confusing, and does not explain the concept of pressure properly...