Answer:
1. Speed is a scalar quantity that refers to "how fast an object is moving." Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a short amount of time.
2. a. The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time.
b. Acceleration is the rate of change of velocity.
3. It can be caused by friction.
Step-by-step explanation: