1. D. velocity
Explanation: Acceleration is best defined as the rate of change of velocity of an object. In fact, acceleration is defined as:
\(a=\frac{\Delta v}{\Delta t}\)
where \(\Delta v\) is the change in velocity of an object, while \(\Delta t\) is the time taken for that change in velocity to occur. Keep in mind that a change in velocity means a change either in the speed of the object, or in its direction: so, for instance when an object moves at constant speed in a circle, it is also accelerating since its direction is changing, and so its velocity is also changing.
2. C. m/s2
Acceleration is measured in \(m/s^2\). In fact, acceleration is defined as
\(a=\frac{\Delta v}{\Delta t}\)
where \(\Delta v\) is measured in m/s, while \(\Delta t\) is measured in s (seconds), so acceleration is measured in
\([a]=\frac{[m/s]}{[s]}=[\frac{m}{s^2}]\)
3. C. Velocity has both speed and direction
In fact:
- speed is a scalar, so it consists only of a magnitude, which is defined as the ratio between the distance traveled (d) and the time taken (t):
\(s=\frac{d}{t}\)
- velocity is a vector, so it consists of both a magnitude (which is the speed) and a direction, which is given by the direction of motion.
