An unknown radioactive element decays into non-radioactive substances. in 420 days the radioactivity of a sample decreases by 39 percent.1.what is the half-life of the element? 2.how long will it take for a sample of 100 mg to decay to 46 mg?

The de broglie relation λ=h/p can be rewritten in terms of the wave number k as p=kℏ. recall that wave number is defined by k=2π/λ. using the fact that λ=v/f, find the wave numbers k1 and k2 corresponding to frequencies f1 and f2. express your answer as two expressions

1.what is where an object is located 2. what is how fast an objects speed is changing 3. what is how fast an object is moving

Individuals who live below the poverty line get seriously ill more often than those who do not what could be the hidden variable in this situation?