Difference between Speed and Velocity

What is the difference between Speed, Velocity and Acceleration? Could any one describe it pictorially?. I am more over confused even after investigating many times. I am unable to relate myself practically.

Speed has no direction while velocity does. For example, if I say that I'm running at 10 mph, I have given you my speed. If I say that I'm running 10 mph north, then I have given you my velocity. Acceleration is the rate of change in velocity. Imagine this: I am in my car and you look at me before I even press the gas pedal. You close your eyes then open them (imagine the blinking only took a second). Now, I'm going 10 mph north. You blink again. Now I'm going 20 mph north. Every second my velocity increased 10 mph north. This means my acceleration is 10 mph every second or 10 mi/h/s.

• for eg: Sometimes we describe the speed of a vehicle to be 60Km/hr to our friends when we mention about the trip details ..Does it really mean the speed?..Isn't it the acceleration or velocity?
– ddpd
Mar 30 '15 at 4:41
• @ddpd yes it means speed Mar 30 '15 at 4:45
• for it to be velociy, there would need to be a direction, so 60 Km/hr north or even 60 Km/hr that way Mar 30 '15 at 4:46
• For it to be acceleration the car needs to keep going faster, or it needs to change direction as shown in the picture Mar 30 '15 at 4:47

Speed is a scalar quantity which means that it is described by only magnitude.

Velocity is a vector quantity which means that it is described by magnitude and direction.

And acceleration is the rate of change of velocity with respect to time.

i. e. Acceleration= $$(V_2-V_1)$$ / Time required to travel this distance