$$ \text{Chapter 1: Velocity and Acceleration} $$

<aside> 🍀 Always know the direction of the object and adding forces that cause the object to go that direction and minus forces that cause object to go in opposite direction.

</aside>

Uniformly accelerated motion equations:

• $s:$Displacement(vector) has magnitude and direction, can be negative
  • Distance(scalar) is displacement’s magnitude, thus can’t be negative
• $v:$Velocity(vector) has magnitude and direction, can be negative
  • Speed(scalar) is velocity’s magnitude, can’t be negative (distance/time)
• $a:$Acceleration measures how quickly velocity is changing, assumed constant
  • ${\color{tomato}-}a$ if deceleration, slow down, decrease speed, gradient of the graph
  • $a$ is positive: speeding up in intended direction or slowing down in opposite direction
  • $a$ is negative: slowing down in intended direction or speeding up in opposite direction
  • Initial and after velocity must be in the same direction
• Write down given numbers and choose suitable formula(e):

$v=u+at$

$s=\frac 1 {2}(u+v).t$

$s=ut+\frac 1 {2}at^2$

$v^2=u^2+2as$

<aside> 🍀 $s=vt{\color{tomato}-}\frac 1 {2}at^2$

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• $a$ can be negative, makes the sign plus
• Not given in the booklet

Displacement-time graph

• The gradient is velocity
• Deceleration has opposite arc of accel
• Can’t have discontinuity

Velocity-time graph

• The gradient is acceleration
• Area under graph is displacement, $s$
• Can have discontinuity (bounce back)
• Break the journey down the many stages and calculate each separately
• It’s useful to sketch graph and write distant equations of 2 different objects to find $t$