Acceleration:a change in Velocity!

An object traveling at the same rate in the same direction, is in uniform motion.

NON uniform motion - there must be an increase or decrease in Velocity.

Acceleration is a vector quantity. It is the rate at which velocity CHANGES with time.

a

Any speeding up, slowing down, or change in the direction of motion means that velocity is changing.

Any of this is acceleration.

a = v t

v = 6 m/s [S]

v = 6 m/s [W]

=

∆t∆va

= vfinal - vinitial

tfinal - tinitial

If a cheetah reaches a speed of 19 m/s in 2.0 s from a standing start, what is the cheetah's acceleration?

= + 9.5 m/s2

v1 = 0 m/s

= ∆t∆v

vfinal - vinitial

tfinal - tinitial

v2 = +19 m/s

a

= 2+19 - 0a

Find the acceleration of a bike as it from +13.9 m/s to +8.3 m/s in 3.5 s.

= - 1.6 m/s2

v1 = +13.9 m/s

= ∆t∆v vfinal - vinitial

tfinal - tinitial

v2 = +8.3 m/s

a

= 3.5+8.3 – (+13.9)a

slows down

A speed skater at the start line accelerates at +4.1 m/s2, and reaches a top speed in 3.2 seconds. What is the change in velocity?

∆v = ?

= ∆t∆v

∆t = 3.2 s

a

a = + 4.1 m/s2

= 3.2∆v4.1 (3.2) = ∆v 4.1 (3.2)+ 13 m/s

a = v t

d = d2 - d1

v = d t

t = t2 - t1

P-T Graph P-T Graph