# [Answer] What is the acceleration? Writing Linear Functions

The magnitude of an object’s acceleration as described by Newton’s Second Law is the combined effect of two causes: • the net balance of all external forces acting onto that object — magnitude is directly proportional to this net resulting force; • that object’s mass depending on the materials out of which it is made — magnitude is inversely proportional to the object’s mass. The SI unit for acceleration is metre per second squared (m⋅s ${\tfrac {\operatorname {m} }{\operatorname {s} ^{2}}}$). For example when a vehicle starts from a standstill (zero velocity in an inertial frame of reference ) and travels in a straight line at increasing speeds it is accelerating in the direction of travel. If the vehicle turns an acceleration occurs toward the new direction and changes its motion vector. The acceleration of the vehicle in its current direction of motion is called a linear (or tangential during circular motions ) acceleration the reaction to which the passengers on board experience as a force pushing them back into their seats. When changing direction the effecting acceleration is called radial (or orthogonal during circular motions) acceleration the reaction to which the passengers experience as a centrifugal force . If the speed of the vehicle decreases this is an acceleration in the opposite direction and mathematically a negative sometimes called deceleration and passengers experience the reaction to deceleration as an inertial force pushing them forward. Such negative accelerations are often achieved by retrorocket burning in spacecraft Read more on Wikipedia
Velocity refers to a displacement in one direction with respect to an interval of time. It is defined as the rate of change of displacement over change in time. Velocity is a vectorial quantity representing a direction and a magnitude of movement. The magnitude of a velocity is called speed. The SI unit of speed is ${\text{m}}\cdot {\text{s}}^{-1}$ that is metre per second. The average velocity of a moving body is its total vectorial displacement \${\dis…