Acceleration and Its Sign
Acceleration is the rate of change of velocity, a = dv/dt, measured in m/s2.
What is Acceleration and Its Sign?
Acceleration is the rate of change of velocity, a = dv/dt, measured in m/s2.
Key formula / rule: a = dv/dt = slope of the v-t graph.
Key points
- Interpret the sign of acceleration relative to the sign of velocity.
- Compute acceleration from a velocity-time record.
Common exam trap
Assuming zero velocity implies zero acceleration.
Definitions
- Term
Acceleration and Its Sign
- Meaning
Acceleration is the rate of change of velocity, a = dv/dt, measured in m/s2.
- Term
Acceleration and Its Sign — explanation
- Meaning
Acceleration describes how velocity changes, not how fast the body moves. A negative acceleration slows a body moving in the positive direction but speeds up a body moving in the negative direction, so 'deceleration' must always be read together with the sign of velocity.
Learning objectives
Interpret the sign of acceleration relative to the sign of velocity.
Compute acceleration from a velocity-time record.
Formulae
- Key point
a = dv/dt = slope of the v-t graph.
- Key point
Speed increases when a and v share a sign, decreases when they oppose.
- Key point
Acceleration can be non-zero while velocity is instantaneously zero (top of a throw).
Prerequisites
PHY-U1-KIN-T1-S1-C2
Common mistakes
Assuming zero velocity implies zero acceleration.
Calling every negative acceleration a slowing-down.
Keywords
Acceleration
Practice preview
What is the SI unit of acceleration?…
easy
A car is moving in the positive x-direction and its speed is increasing. What is the sign of its acceleration?…
easy
A ball is thrown vertically downwards. Assuming the upward direction is positive, what is the sign of its acceleration due to gravity?…
medium