MOVING+WITH+CHANGING+VELOCITY

Back to IGCSE PHYSICS > FORCES AND MOTION > MOVEMENT AND POSITION
 * ~ 1 FORCES ||~ 2 ELECTRICITY ||~ 3 WAVES ||~ 4 ENERGY ||~ 5 SLG ||~ 6 MAGNETISM ||~  ||

=MOVEMENT AND POSITION=
 * MOVING WITH CONSTANT VELOCITY || **MOVING WITH CHANGING VELOCITY** ||

1.4 recall and use the relationship between acceleration, velocity and time:

VELOCITY: the distance travelled in unit time in a stated direction. Velocity is a vector. Units can be m/s km/h etc UNIFORM or CONSTANT: When a quantity does not change in magnitude or direction. DISPLACEMENT: Distance moved in a stated direction. Vector. Unit: metre (m). ACCELERATION: The change in velocity in unit time. Vector. Unit usually m/s 2

EXAMPLE 1 Find the acceleration of a car which speeds up from 14 m/s to 30 m/s in 10 s.

EXAMPLE 2 A rocket slows down from 1000 m/s to 400 m/s in half a minute. What is its acceleration?

EXAMPLE 3 A runner accelerates at 1.5 m/s 2 for 5 seconds, starting at 2.5 m/s. What is his final velocity?



[|LYRICS TO SPEED AND VELOCITY BY THEY MIGHT BE GIANTS]

**VELOCITY-TIME GRAPHS**


ACTIVITY: Which lines on a v-t graph correspond to which descriptions?

1.5 interpret velocity-time graphs 1.6 determine acceleration from the gradient of a velocity-time graph 1.7 determine the distance travelled from the area between a velocity-time graph and the time axis.

THIS GRAPH CAN BE USED TO CALCULATE ACCELERATION AND DISTANCE TRAVELLED FOR EACH STAGE OF MOTION a 1 = (0-0)/2 = 0 m/s 2 a 2 = (20-10)/(5-2) = 3.3 m/s 2 a 3 = (14-20)/(10-5) = -1.2 m/s 2
 * ACCELERATION**


 * NOW CALCULATE THE ACCELERATION OF EACH STRAIGHT LINE ON THE GRAPHS A-F BELOW**

d 1 = 2*10 = 20 m d 2 = 3*10 + 3*10/2 = 45 m   d 3 = 5*14 + 5*6/2 = 85 m
 * DISTANCE TRAVELLED**


 * d total = 20 + 45 + 85 = 150 m **


 * NOW CALCULATE THE DISTANCE TRAVELLED DURING EACH STAGE ON THE GRAPHS A-F BELOW**

ACTIVITY: Calculate accelerations and distances travelled from the following v-t graphs: