Chapter 9 - Constant Acceleration Flashcards
Displacement-time graphs:
- You can represent the motion of an object on a displacement-time graph. Displacement is always plotted on the vertical axis and time on the horizontal axis
- In these graphs s represents the displacement of an object from a given point in metres and t represents the time taken in seconds
Stationary objects on a displacement-time graph:
Objects moving with constant speed/velocity on a displacement-time graph:
Accelerating objects on a displacement-time graph:
What is velocity:
The rate of change of displacement
What does the gradient represent on a displacement-time graph?
Velocity
Average velocity =
displacement from starting point/time taken
Average speed =
total distance travelled/time taken
Velocity-time graphs:
- You can represent the motion of an object on a velocity-time graph. Velocity is always plotted on the vertical axis and time on the horizontal axis
- In these graphs v represents the velocity of an object in metres per second and t represents the time taken in seconds
Stationary object on a velocity-time graph:
An object moving with constant velocity on a velocity-time graph:
An object moving with increasing velocity and constant acceleration on a velocity-time graph:
What is acceleration?
The rate of change of velocity
What does the gradient represent in a velocity-time graph?
Acceleration
If the velocity-time graph has a straight line…
the acceleration is constant
What does the area between a velocity-time graph and the horizontal axis represent?
The distance travelled
How to find the displacement of a velocity-time graph at time t?
For motion in a straight line with positive velocity, the area under the velocity-time graph up to a point t represents the displacement at time t
s:
u:
v:
a:
t:
(in relation to velocity-time graphs)
s: displacement
u: initial velocity
v: final velocity
a: acceleration
t: time
How to find:
Deriving constant acceleration formulae: eliminating t
Deriving constant acceleration formulae: eliminating v
Deriving constant acceleration formulae: eliminating u
The suvat equations/constant acceleration formulae:
Vertical motion under gravity:
The force of gravity causes all objects to accelerate towards the earth. If you ignore the effects of air resistance, this acceleration is constant. The acceleration does not depend on the mass of the object
g:
An object moving vertically under gravity can be modelled as a particle with a constant downward acceleration of
- g = 9.8 ms-2
(answer must be to the same number of d.p. of g used)
