[mahmoud khodary]

1 - Ans. c

mass = volume * density
volume = area * height
area = pi * r^2
m = 730 * 3.14 * 0.013^2 * 0.2
m = 77.48 *10^-3 kg
m = 77.48 g

2 - Ans. c

the density of the solid sphere is much higher than the density of water so it goes down to the bottom
and the tension in the cord is equal to the weight of the solid sphere
W = T = m *g = 3.4 *9.81
T = 33.33 N

3 - Ans. a

pressure = density * gravitational acceleration * column height
p = 1025 * 9.81 * 8000
p = 80442 Pa
force = pressure * area
area = pi * r^2 = 3.14 * 0.94^2 = 2.77 m^2
F = 80442 * 2.77
F = 2.23 *10^8 N