Why does the frequency of a siren get higher as an ambulance using that siren gets closer?

The 10-kg double wheel with radius of gyration of 125mm about o is connected to the spring of stiffness k = 600 n/m by a cord which is wrapped securely around the inner hub. if the wheel is released from rest on the incline with the spring stretched 225 mm, calculate the maximum velocity v of its center o during the ensuing motion. the wheel rolls without slipping

Your science teacher brings in a speaker to talk to your class about climate change. during the session, students ask a few questions. which questions are related to the current evidence on climate change

Amagnetic field applies forces on: a)static chargesb)moving chargesc)water flow