In lab you find that a 1-kg rock suspended above water weighs 10 N. When the rock is suspended beneath the surface of the water, the scale reads 8 N.
a. What is the buoyant force on the rock?
b. If the container of water weighs 10 N on the weighing scale, what is the scale reading when the rock is suspended beneath the surface of the water?
c. What is the scale reading when the rock is released and rests at the bottom of the container?
a) 2 N
b) 12 N
c) 20 N

a. 2N

b. 12N

c. 20N

Explanation:

Dtaa given,

Weight of rock in air=10N

weight of rock in water =8N

a. When the rock is suspend in water, it will displace some water from thr container since Buoyant force is the acts upward and equals in magnitude to the volume of water displays,

The buoyant force is calculated as 10N-8N=2N

b. The scale reading will be the sum of the buoyant force and the weight of the container

scale reading =10N+2N=12N

c. When the rock rest at the bottom of the container, the weight of the rock(10N) is acting downward and the weight of the container also is acting downward. Hence the sum of the two weight gives the reading on the scale

scale reading=10N+10N=20N

0.19 m/s and 0.45 m/s