Suppose you have 50 grams of a radioactive isotope with a half-life of 2 years. how much of the isotope will you have after 4 years?
a. 50 g
b. 25 g
c. 12.5 g
d. 6.25 g

Abearing is designed to a reduce friction b. support a load c.guide moving parts such as wheels, shafts and pivots d. all of the above

Adding more pulleys to a system of pulleys needed to lift an object. a. increases the force b. decreases the force c. increases the amount of work d. decreases the amount of work

If a tank filled with water contains a block and the height of the water above point a within the block is 0.8 meter, what is the pressure at point a?