Chapter 2~ Accelerated Motion Flashcards
Key ideas 💡, definitions and formula
Definition of acceleration
°the rate of change in velocity
Formula for acceleration =
a=🔼v/ 🔼t
🔼v stands for
The change in velocity.
🔼v = v (final) - u(initial)
Any object has acceleration if (2)
- it’s speed is changing
* changing its direction
Unit of acceleration
ms-2
Gradient of a velocity time ⌚ graph =
Acceleration
A straight line with a positive slope on a velocity time ⌚ graph represents
Constant acceleration
The steeper the slope of a v-t graph…
The greater the acceleration
When the gradient on a v-t graph is zero. It means two things
- velocity is constant
2. Therefore acceleration =0
A negative slope on a v-t graph means
Deceleration
If the slope is changing on a v-t graph it means
Acceleration is changing
The area under a v-t graph equals?
➕ formula
Displacement
Area =1/2 x b x h
Sometime is a rectangle A= L x B
(sometimes you have to count the ‘squares’ under the graph)
The 4 equations of motion:
- v= u + at
- v^2= u^2 +2as
- s= ut + 1/2at^2
- s= (u+v/2) x t
The 4 equations of motion can only be used for 2 things namely:
- Motion in a straight line
2. For an object with constant acceleration
The 4 equations of motion can only be used for 2 things namely:
- Motion in a straight line
2. For an object with constant acceleration
How to derive the first equation of motion:
v= u + at
2 steps :
- Acceleration is defined as the rate of change in velocity :
a= v-u/t
- Rearrange this to get v as the subject of the formula :
v =u +at
How to derive s=((u+v) /2)x t
2 steps
- Displacement =the average velocity x time taken (defined from v =d/t)
- Average velocity = (v+u) /2
Therefore :
s= ((u+v) /2) x t
How to derive s = ut +1/2at^2
3 steps :
Step 1: We need 2 equations :
- v=u+at
- s= ((u+v) /2)x t
Step 2: Sub v from equation 1 in equations 2’s v
s= ((u+u+at) /2)x t
s=(2ut)/2 +(at^2)/2
Step 3: simplify
So s= ut + 1/2 at^2
How to derive v^2 =u^2 + 2as
3 steps :
- Use two equations :
One : v= u+at
Two : s= ((u+v)/2)x t
- Sub t in from equation one
s= ((u +v) /2) +((u-v) /a)
Step 3
Rearrange to get 2as =(u+v) (v-u)
Then v^2 = u^2 +2as
For s=ut +1 /2at^2
What 2 equations do you use and what do you substitute?
Equations: v =u +at
s= ((u+v) /2) x 2
Sub v in from equation one in equation two
v^2 = u ^2 +2as
What 2 equations do you use and what do you substitute in?
Equations : v = u +at
s = ((u+v) /2) x t
Sub in t from equation one into equation two
What is acceleration caused by gravity
9.81ms-^2
The vertical motion of an object is affected by 1 things :
- Weight
The horizontal component is unaffected by?
Gravity
In the absence of air resistance, the object has a constant velocity in the horizontal when means….
No acceleration
To find the component of any vector (e.g. Displacement, velocity, acceleration, etc) in a particular direction, there are 2 steps :
And the equation
Step 1:
find the angle🎈 between the vector and the direction of interest
Step 2 :
Multiple the vector by cosine of the angle🎈
vcos🎈
Definition of terminal velocity
The maximum velocity of an object travelling through a fluid. The resultant force on the object is zero. (when the weight of the object = the air resistance)
Definition of lost volts
The difference between the e.m.f. and the terminal p.d in a circuit. It is equal to the voltage ⚡ across the internal resistance.
