The graph below shows the position of a toy over time, measured using photogates.

at which of the labeled points is the car's velocity at a single moment lowest?

a. point a
b. point b
c. point c.
d. point d.

Point C.

.

is the same as the gradient of the tangent to the position-times graph at the point in question.

Draw a tangent line to the curve at each point. Measure the gradient of each tangent line. The gradient of the tangent line to the curve is smallest at point C among all four points. Therefore, the car's velocity is smallest at point C.

see earlier answer

c) up is the direction the magnetic force is acting on the charge.