at a certain time, an object in free fall has velocity of 4m/s in upwards direction. What is the velocity of the object one second later?

Explain vector addition, triangle method and parallelogram method

What was the first instrument to ever record an earthquake?

Two point charges are separated by a certain distance. how does the strength of the electric field produced by the first charge, at the position of the second charge, change if the second charge is doubled? a. the field does not change b. the field strength decreases by half. c. the field strength doubles d. the field strength quadruples