một vật dao động điều hòa có T=1s, lúc t=5,25s khi x=2,5√3 (cm) và v=5pi (cm/s). viết phương trình dao động

20) what is a magnetic field? 21) in which direction do magnetic field lines always point? 22) sketch a diagram showing how a plotting compass points around a 23) name two magnetic poles that will: a) attract each other b) repel each other. 24) explain why you can use a compass to navigate. 25) what's an electromagnet? 26) list two ways to increase the strength of an electromagnet. 27) the wire in a simple motor feels a force when a current flows through it. why is this? i need answers to check mine