# ACCELERATION Acceleration Acceleration is a vector which measures

• Slides: 15

ACCELERATION

Acceleration • Acceleration is a vector which measures the change in the velocity of an object. • It has magnitude and direction.

This means acceleration could be any of the following three… 1. A change in speed; the magnitude of the velocity (Ex: from 34 km/h to 67 km/h) 2. A change in direction (Ex: from East to North East) 3. A change in both speed and direction (Ex: from 34 km/h East to 12 km/h West)

Acceleration • Acceleration is a measure of the RATE at which velocity changes. • Since velocity is a measure of the rate of change in displacement and had the equation…… V=d t

Average Acceleration Equation • The equation for Average Acceleration should be similar, since it is a rate of change in velocity… a = Δv Δt a = acceleration (m/s/s or m/s 2) Δv = change in velocity (m/s) Δt = time interval (s) • m/s/s = What this really means is that for every second that passes the velocity of the object will change by this many meters per second.

Constant Acceleration • An object is moving at constant acceleration if it is changing its velocity by the SAME amount each second.

Acceleration that is not Constant

Positive vs Negative Acceleration • Since acceleration is a vector quantity, it has a direction associated with it. The direction of the acceleration vector depends on two things: vwhether the object is speeding up or slowing down vwhether the object is moving in the + or - direction • The general principle for determining the acceleration is: • If an object is slowing down, then its acceleration is in the opposite direction of its motion.

Positive Acceleration – 2 ways

Positive Acceleration – 2 ways • Explanation: • In A, the object is moving in the positive direction (positive velocity) and is speeding up. • When an object is speeding up, the acceleration is in the same direction as the velocity, so a positive acceleration.

Positive Acceleration – 2 ways • In B, the object is moving in the negative direction (negative velocity) and is slowing down. • When an object is slowing down, the acceleration is in the opposite direction as the velocity, so a positive acceleration.

Negative Acceleration – 2 ways

Negative Acceleration – 2 ways • Explanation: • In C, the object is moving in the positive direction (positive velocity) and is slowing down. • When an object is slowing down, the acceleration is in the opposite direction as the velocity, so a negative acceleration.

Negative Acceleration – 2 ways • In D, the object is moving in the negative direction (negative velocity) and is speeding up. • When an object is speeding up, the acceleration is in the same direction as the velocity, so a negative acceleration.

Symbol Reminders • In physics (+) and (-) describes a direction • Negative accelerations do not mean values that are less than zero • Ex: -2 m/s 2 = means an acceleration of 2 m/s 2 directed in the negative direction