The slope of a speed-time linear graph is acceleration direction speed velocity

The answer is acceleration because the slope is how the sharp or steep the speed is increased. In a velocity versus time graph, any small part of the curve can be written as V = m T + b; where the slope of the curve is equals to dV/dT. b = U is the primary speed when time is equals to 0. In physics, the change in velocity over an interval of time is defined as acceleration.

Answerwavelength;

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.