A 0.40 kg block can slide up and down a rough a 10-m-high, 30-m-long slope. At the bottom, a stiff spring with spring constant 800 N/m is compressed 0.50 m and used to launch the block up the slope. The friction force on the block from the slope is 1.2 N. What is the speed of the block when it reaches the top of the slope, in m/s

Independent variable is something that is changed in a experiment. 

Answer: 1.4 seconds which is the third optionexplanation: current is defined as the flow of charge per timetherefore, the equation that relates current, charge and time can be expressed as follows: i = δq / δtwhere: i is the current given = 1.8 ampereδq is the charge given = 2.5 coulombδt is the time required for the flow of the given charges to give the 1.8 ampere.substitute with the givens in the above equation to get the time as follows: 1.8 = 2.5 / δtδt = 2.5 / 1.8 = 1.38888 which is approximately 1.4 secondshope this was !