The half-life for an 80-gram sample of an unknown radioactive element is 5 days. How much of the unknown radioactive element remains after 10 days have passed?

A. 20 g

B. 40 g

C. 70 g

D. 80 g

Pls help, I'll mark brainiest, I really need a good grade, so pls answer correctly.

When applying kirchhoff's rules, one of the essential steps is to mark each resistor with plus and minus signs to label how the electric potential changes from one end of the resistor to the other. the circuit in the drawing contains four resistors, each marked with the associated plus and minus signs. however, one resistor is marked incorrectly. which one is it?

A100 kg running back runs at 5m/s into a stationary linebacker. it takes 0.5 for the running back to be completely stopped

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?