2.8–2.9: Acceleration equations

What is acceleration?

The rate of change of velocity.

What is the equation for acceleration?

Acceleration = change in velocity ÷ time taken.

Write the acceleration equation using symbols.

a = (v − u) ÷ t.

What does a represent in the acceleration equation?

Acceleration, in m/s².

What does v represent?

Final velocity, in m/s.

What does u represent?

Initial velocity, in m/s.

What does t represent?

Time taken, in seconds.

What is the unit of acceleration?

Metres per second squared (m/s²).

What is the equation linking velocity, acceleration and distance?

v² − u² = 2as.

What does s represent in v² − u² = 2as?

Distance travelled, in metres.

When can you use v² − u² = 2as?

When acceleration is constant.

A car accelerates from 5 m/s to 25 m/s in 4 s. Calculate its acceleration.

a = (25 − 5) ÷ 4 = 5 m/s².

A cyclist accelerates at 2 m/s² for 6 s from rest. Find the final velocity.

v = u + at = 0 + (2 × 6) = 12 m/s.

An object accelerates from 4 m/s to 10 m/s in 3 s. Calculate its acceleration.

a = (10 − 4) ÷ 3 = 2 m/s².

A car starts from rest and accelerates at 3 m/s² over 24 m. Calculate its final velocity.

v² = u² + 2as = 0 + (2 × 3 × 24) = 144; v = 12 m/s.

What is deceleration?

Negative acceleration; the velocity changes in the opposite direction to the acceleration, so the object slows down.