An oscillator makes 20 vibrations in 2 seconds. What is its period and frequency?

Which type of wave can travel without a medium

The force needed to overcome static friction is usually less than that needed to overcome kinetic friction.true or false?

Aprisoner is forced to go into one of three rooms, but he can choose which room. the first room is ablaze with fire. the second one is rigged with explosives that will go off as soon as he enters. the third contains a pair of lions who haven't eaten in years. which room should he choose to survive?