Solve the following half-life problems. 1. The half-life of Pa-234 is 6.75 hr. How much (what fraction) of a sample of this isotope remains
after 20.25 hr?

2. The half-life of Rn-222 is 3.823 day. What was the original mass of a sample of this isotope if
0.0500 g remains after 7.646 day?

3. The half-life of Th-227 is 18.2 day. How many days are required for 0.70g of a given sample to
decay to 0.0875 g?

4. The half-life of carbon-14 is 5700 years. If a 10 gram sample undergoes decay for 17,100 years,
how many half-lives have the sample undergone?

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.

Is this a question of an answer

Answer: a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same sign as the  -4.0  µc charge.======electricstatic force between two point charges  is given by    where k is coulomb's constant,  8.99×10⁹  n·m²/c², q₁ and q₂ are the point charges, and r is the distance between the two point charges.assign positive to q₁let q₁ =  6.0 µc, q₂ = -4.0  µc, q₀ represent the charge at the origin, and q₃ represent this new charge to place.the charge at the origin q₀ would experience the following force f₀₁ from q₁, with r = 6.0 m (note that 1  µc = 10⁻⁶ c)    the force from q₂    the force from q₃    the net force on the origin charge, q₀, has to be zero for no electrostatic forcehaving an equation where k and q₀ can be divided out of the equation will allow us to solve for q₃    isolating:     a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same as the  -4.0  µc charge