Velocity of Volcano Ejecta

[Ice-cream]

A volcano ejects a lava bomb straight upward with an initial speed 23m/s. Taking upward to be the positive direction, find the speed and velocity of the lava bomb a) 2 seconds b) 3 seconds

 

(Ans: a)3.4m/s, 3.4m/s b) 6.4m/s, -6.4m/s)

 

i don't understand why the speed and velocity are both positive for a) but for b), the velocity is negative but the speed is positve. can any1 explain to me plz? thanx

[Sayonara]

Speed is a scalar quantity - it has only magnitude.

 

Velocity is a vector quantity - it has both magnitude and direction.

 

So the negative velocity represents motion in the opposite direction to the positive velocity.