7.7 Projectile motion 1 Flashcards
What is a projectile
Any object acted upon only by the force of gravity
What are the three key principles that apply to all projectiles
1 - The acceleration of the object is always equal to g and is always downwards because the force of gravity acts downwards. The acceleration therefore only affects the vertical motion of the object
2 - The horizontal velocity of the object is constant because the acceleration of the object does not have a horizontal component
3 - The motions in the horizontal and vertical directions are independent of each other
If the initial projection of a stone thrown from a cliff top is horizontal:
Its path through the air becomes steeper and steeper as it drops
The faster it is projected, the further away it will fall into the sea
The time taken for it to fall into the sea does not depend on how fast on how fast it is projected
If one ball is dropped vertically but the other is projected horizontally, which will land first
They land simultaneously
They experience the same downward acceleration g, this does not affect the horizontal motion of the ball, only the vertical motion is affected
What can be used to record the motion of a projectile
A stroboscope and a camera with a slow shutter
Projectile path of a ball projected horizontally
Horizontal component of its displacement
x=Ut
Vertical component of its displacement
y=1/2 gt^2
In which:
U - initial velocity
t - time after projection
At time t, the speed = (v^2 x + v^2 y)^1/2