Mechanics Grade -12

Mechanics Grade -12

Velocity time Graph

• Objectives

• To relate the shape (horizontal line, diagonal line, downward-sloping line, etc.) of a velocity-time graph to the motion of an object.

• To relate the slope value of the line on a velocity-time graph at a given time or during a given period of time to the instantaneous or the average velocity of an object and to determine such velocity values using a slope calculation.

• To relate the area between the line and the time-axis of a velocity-time graph to the displacement of the object and to determine such displacement values using an area calculation.

Poll

In velocity time graphs time is taken on

• X-axis

• y-axis

• time is not considered

Poll

In velocity time graph velocity can be taken on

• Only positive y axis

• Only negative y-axis

• positive and negative y-axis

• x-axis

Multiple Select

In velocity/time graph Acceleration can be calculated...

• by area under the graph

• Gradient of the line

Open Ended

Where in daily life is speed /time or velocity /time seen?

Open Ended

Can you relate this graph with any other subject and how?

SHORT VIDEO

https://www.compadre.org/physlets/mechanics/ex2_1.cfm

Open Ended

For Animation 1 write

Initial Velocity

Acceleration

Red Green Blue

Open Ended

For Animation -2 write

Initial Velocity, Acceleration

Red Green Blue

Open Ended

For Animation - 3 write

Initial Velocity

Acceleration

Red Green Blue

Lets solve some examples

The diagram shows the speed time graph of the motion of the athlete running along the straight track. For the first 4 seconds, he accelerates from 0m/s to 9m/s The velocity is than maintained for a further of 8 seconds.

a. find the rate at which athlete accelerates.

b. The displacement from the starting point after 12sec.

NOW ITS YOUR TURN

Graph shows a journey of a cyclist along a straight road

a. Find the acceleration in first 10 seconds.

b. Deacceleration in last 15 seconds.

c. Displacement in 75 seconds.

d. Average speed of the cyclist.

Open Ended

Plenary

What did you learn today?

Home-work

EX-2B

Q. 2, 4,5,6,7,8