Which of the following is a speed, not a velocity?

A.

35 m/s east

B.

-35 m/s

C.

35 m/s

D.

35 m/s south

Velocity is a vector quantity which means that it has both magnitude and direction.

Speed is a scalar quantity which only is defined by its magnitude.

(magnitude refers to its numerical value or absolute value)

Because speed is a scalar quantity it will not have a direction which means that answer A and answer D are wrong because they have the direction of east and south. The answer is choice C. 35m/s and not B. - 35m/s because speed cannot be a negative value. (note that while speed cannot be negative velocity can)