If a 20 kg box is accelerating upward at 8 m/s^2 , what is the magnitude of the upward force

356 N

Explanation:

Newton's second law of motion describes the relationship between an object's mass and the amount of force needed to accelerate it.  

here there is a weight acting downwards on the object , yet it is accelerating  upwards shows that there is a net force upwards

Applying Newtons second law of motion upwards ,

Force  = mass *acceleration

Upward force - m*g = m *a

F_up= 20 *8 + 20 * 9.8

         = 356 N

Upward force= 160 N

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.