Quiz on Free Responses

Journal:

1. As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it? Explain?

1. It remains constant.

2. Consider three drinking glasses.  All three have the same area base, and all three are filled to the same depth with water.  Glass A is a cylindrical.  Glass B is wider at the top than at the bottom and so holds more water than A.  Glass C is narrower at the top than at the bottom and so holds less water than A.  Which glass has the greatest liquid pressure at the bottom? Explain?

2. All three have equal pressure. Pressure is a function of depth and density of the liquid.

3. Calculate the period of a pendulum that has a length of 4.0m  & 16.0m on Earth and Planet X where acceleration of gravity is 2m/s²

3.  Earth

p = 2 √ L  = 2 √ 4  = 4s

    p = 2 √ L  = 2 √ 16  = 8s

Planet x

p = 2 p √ (L/g_x)  = 2 p√ (4/2)  = 8.9s

p = 2 p √ (L/g_x)  = 2 p√ (16/2)  = 17.8s

4. A metal ball (Fe) sinks in water but floats in a pool of mercury.  Where is the buoyant force on the ball greater? Explain

5. 50 cm³ of wood is floating on water (90% submerged), and 50 cm³ of Pb is totally submerged.  Which has the greater buoyant force on it? Explain

4. Floating: If floating, the Buoyant force is equal to weight of the object. If sunk, Buoyant force is less than weight of object.

5. Pb

50 cm³ wood floating displaces less water than 50 cm³ Pb that sinks. Buoyant force is equal to weight of the displaced water. The greater the  displaced water, the greater the Buoyant force (i.e. Pb)