My doubts: 1. Why doesnt the time period of a simple pendulum depend either on mass or on the magnitude of amplitude? 2.Why is pressure regardeed as a scalar quantity? I cant say anything about the first question. But about the second I'll share my views. Pressure = Force/ Area : Force is vector and 1/Area is scalar. So their product should be a vector. There was one more question regarding this in my book, A very thin foil of a metal is placed at a certan depth in water. My book states that it will remain in that position (it will niether rise up nor will sink down) because pressure acts on both sides is equal in magnitude but opp. in direction. If pressure has a direction, then why is it scalar? This is really confusing. 3. For fluids the magnitude of pressure is given by hdg. Why isnt it applicable for solids? For solids as well: A*h*d*g/A =Pressure.