Calculate the force exerted on a 10 kg object accelerating from rest to 10 m/s in 1.5 seconds

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

Where do magnetic lines of force enter earth?

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.