22/02/2020
(Summary Set For Grade 12)
PROJECTILE MOTION (VPM)
Complied By :Mahlatse The Best Tutor
*WHAT GOES UP MUST COME DOWN*
all objects are attracted to the earth with a gravitational force called *WEIGHT*
all objects will accelerate towards the earth with a constant acceleration called the *_Gravitational acceleration (g)_*
Gravitational acceleration is *ALWAYS downwards* no matter wether the object is being thrown up or falling down
*IMPORTANT:*For any object thrown up or down, the first direction is taken as positive (+)
*Check the equation of motion in your textbook and substitute (a) with (g)*
```Important facts on VPM```
At the greatest height of the upward motion, *velocity of the object is ZERO*
The object will take the *same time* to reach it's greatest height form point of upward launch as the time taken to fall back to point of launch
*( Time Up = Time Down )*
Can have motion described by a single set of equations of motion for the upward and downward motion
You must be able to :-
1.Explain what is meant by a *projectile*, *Free Fall* and *Terminal velocity*
*Terminal Velocity - air resistance (or air friction) have the same magnitude as the weight of the object*
*Projectile - an object upon which the only force acting is the force of gravity*
2.Use equations of motion to determine *Position, velocity and displacement* of a projectile at any given time
3.Learn how to sketch position versus time *(x vs t)*, velocity versus time *(v vs t)* and acceleration versus time *(a vs t)* graphs for :-
*-a free falling object*
*-an object thrown vertically down*
*-an object thrown vertically up*
*Bouncing objects*```(restricted to balls)```
For a given *X vs T* or *A vs T* graph, determine:
*-Position*
*-Displacement*
*-Velocity or acceleration at any time t*
For a given *X vs T* or *A vs T* graph, describe the motion of the object
*-Bouncing*
*-Thrown vertically up*
*-Thrown vertically down*
```You must also note this```
1.Provided there is no friction, the total enery of a free falling body remains constant
2.Concepts :Acceleration, velocity, change in position are all vectors *(Direction is indicated)*
3. *_DROP_* means the initial velocity is *ZERO*
4. *in graphs the acceleration is uniform*
*REMEMBER TO CHOOSE DIRECTION EVERY TIME YOU SOLVE 2D VPM PROBLEMS*
