Because your body displaces some of the water and there is no place for it to go except higher in the tub.
I assume you mean when you turn on the sink water comes up from the drain in the tub? If that's the case, the drain from the tub is clogged. The sink is higher than the tub so the water comes up there.
If the water is draining faster than the spigot is supplying water, the water level in the tub will decrease until the drain and spigot reach equilibrium. This may result in an empty tub if the drain efficiency is higher than the spigot's flow rate.
You can effectively protect your tub from water damage by installing a tub water guard, which is a waterproof barrier that prevents water from leaking out of the tub and causing damage to the surrounding area.
A tub corner splash guard is designed to prevent water from splashing out of the tub by creating a barrier at the corner of the tub where water tends to splash the most. It helps contain the water within the tub, reducing the amount of water that spills out onto the floor.
A tub water diverter is a valve that controls the flow of water between the tub faucet and the showerhead. When the diverter is turned or pulled, it redirects the water flow from the tub faucet to the showerhead, allowing you to switch between filling the tub and taking a shower.
Empty the water out and scrub the tub clean.
The amount of water that evaporates from a hot tub varies based on factors such as temperature, humidity, wind speed, and surface area. On average, a hot tub can lose about 1 to 2 inches of water per week due to evaporation. Higher temperatures and lower humidity levels can increase this rate significantly. To minimize evaporation, using a hot tub cover when not in use is recommended.
To determine if your tub is leaking from the overflow drain, fill the tub with water and observe if the water level rises above the overflow drain. If water is leaking from the overflow drain while the tub is filled, then it is likely that the tub is leaking from the overflow drain.
run hot water and soap in the tub and scrub
Your mass, the mass of the tub and the specific gravity of the water do not change, whether you are in the tub or not.
It will move from one tub to the other. What is it you want to know?
A pot of hot water would melt ice faster than a tub of warm water because the higher temperature difference between the ice and the hot water allows for quicker heat transfer. The hot water has more thermal energy to transfer to the ice, causing it to melt faster.