Asample contains 24 g of a radioactive isotope. how much radioactive isotope remains in the sample after 2 half-lives?

a. 3 g
b. 6 g
c. 12 g
d. 1.5 g

Three point charges, two positive and one negative, each having a magnitude of 20 μc are placed at the vertices of an equilateral triangle (30 cm on a side). what is the magnitude of the electrostatic force on the negative charge

50 g of ice at 0°c is dropped in a beaker containing 100 g of water at 0°c. what will be the contents of the beaker after 5 hours? assume that the room temperature is 0°c.

Find v(t), given acceleration a(t)=7j and initial velocity v(0)=k