A sample contains 20 kg of radioactive material. The decay constant of the material is 0.179 per second. If the amount of time that has passed is 300 seconds, how much of the of the original material is still radioactive? Show all work

Can someone explain to me how to do this problem ?

This problem has been solved! see the answera non-uniform fire escape ladder is 6.0m long whenextended to the icy alley below. it is held at the top by africtionless pivot, and there is neglibible frictional force fromthe icy surface at the bottom. the ladder weighs 250n, and it'scenter of gravity is 2.0m along the ladder from the bottom. amother and child of total weight 750n are on the ladder 1.5m fromthe pivot. the ladder makes an angle θ with the horizontal.find the magnitude and direction ofa) the force exerted by the icy alley on the ladderb) the force exerted by the ladder on the pivotc) do your answers in part a and b depend on the angle?

Anonzero net force acts on a particle and does work. which one of the following statements is true? the kinetic energy of the particle changes, but the speed of the particle does not change. the kinetic energy of the particle does not change, but the speed of the particle does change. the kinetic energy of the particle changes, but the velocity of the particle does not change. the kinetic energy and the speed of the particle change, but the velocity of the particle does not change. the kinetic energy, speed, and velocity of the particle change.