Summary Equations of Motion

EQUATIONS OF MOTION
U =
a + at u= initial velocity Cm 5 ) .
'




' ✓ final (m
'
)
velocity 5
=




at that
.




s = +
a =
acceleration ( m 5) .




t= time ( s)
v2 =
U21-2AS S =
displacement ( m)


( E) t
"
5-

These
equations can ONLY be used for LINEAR MOTION (straight line) and if the object is moving
with a CONSTANT ACCELERATION (a--0 or a
=
constant)




Remember :




U , V , a and s vector need DIRECTION (by
quantities sign)
→
are
giving
•
a



↳ U and :
direction / sign of direction / of
motion
sign velocity
=
v

↳ 5 :
direction of straight line from start to end =
direction of displacement

↳ a "
moves faster → direction of a =
same as direction of motion

slows down → direction of a
=
opposite to direction of motion

•

always choose ref .
frame
•
t → is scalar

be
negative
→
can never

•
If an
object → moves from rest :
4=0

→ comes to rest :
v=O

with constant
→
velocity
:
u=v 9=0
moves ;
•
If an
object makes 2 different motions (eg accelerating from rest and then
moving with constant velocity)
DO 2 SEPARATE CALCULATIONS

If need to determine if will collide with make
object
•


stationary object
→
v=0
you an a


→
find s and compare (< I > than

distance available up to object)
Reaction
'




time driver is not
breaking constant
velocity
•
> → u=u =
-
. .

-




a =
0

E- reaction time

5- ? (reaction distance)

for
Calculate reaction and braking (time distance)
separately combine
stopping ( t Is )
• +
,


•
ALWAYS do a data list (with unit + sign) (convert units if needed )

For linear

]
•
motion distance displacement for distance
'
→
: - =
calculate s when asked
direction / sign
. .




no
for speed
velocity speed (scalars)
'

- = → .
. calculate v when asked