Accelerationand

non-uniform motion

P-T Graph P-T Graph

Changing velocities means it is NON-uniform motion - this means the object is accelerating.

m/s2m/s /s OR=

∆t∆va

P(m

)

t(s)

Origin- +

P(m

)

T(s)

P - T Graph

+ slope

Positive (+) Straight line Moderate slope

Moving to the rightUniform (+) velocitySlow velocity

Origin- +

P(m

)

T(s)

P - T Graph

+ ↑ slope

Positive (+)Increasing slope

Moving to the RIGHTIncreasing (+) velocity(+) Acceleration

Origin- +

- ↑ slopeP

(m)

T(s)

P - T Graphd1d2

Negative (-)Increasing slope

Moving to the LEFTIncreasing (-) velocity(-) Acceleration

Origin- +

+ ↓ slopeP

(m)

T(s)

P - T Graphd2d1

Positive (+)Decreasing slope

Moving to the RIGHTDecreasing (+) velocity(-) Acceleration

Origin- +

- ↓ slopeP

(m)

T(s)

P - T Graph d1d2

Negative (-)Decreasing slope

Moving to the LEFTDecreasing (-) velocity(+) Acceleration

The Sign of Acceleration

Velocity and Acceleration have SAME sign: object is SPEEDING UP

Velocity and Acceleration have OPPOSITE sign: object is SLOWING DOWN

· Acceleration is calculated as the change in velocity over the change in time.

· Acceleration has units of distance/time/time such as m/s/s (m/s2)

· Acceleration is a vector quantity.

Velocity

Acceleration

AND

Keywords

Average velocityInstantaneous velocity

PO

SIT

ION

(m

)

TIME (s)

10

20

30

40

50

5 10 15 20 2500

v = 2 m/s [E]

v = - 1517.5 - 7.5

Uniform motion - average velocity is the same as instantaneous velocity on a P-T graph.

Instantaneous velocity is the velocity of an object at a specific instant in time.

35 - 025- 050

PO

SIT

ION

(m

)

TIME (s)

10

20

30

40

50

5 10 15 20 2500

To find velocity for a specific time, you must estimate by making a straight line at that point.

Slope of this line gives instantaneous velocity for that specific time on the curve.

PO

SIT

ION

(m

)

TIME (s)

10

20

30

40

50

5 10 15 20 2500

A P-T graph with a changing slope means motion with changing velocity (non-uniform / acceleration)

v = + 2 m/s

v = + 5 m/s

Motion is described in words.

Motion is described with a (data) table of values.

Motion is described with a graph.

Motion is describe with equations.

The study of motion (Kinematics) involves: Position, Velocity, Acceleration