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3.2 Accelerate!
A plane takes off at Changes in velocity
Atyrau and flies to In Unit 2 we learnt about how an object can change its velocity (speed)
Oskemen. What is over time. We called it speeding up or slowing down. But in Physics we
the difference in the should talk about this change of velocity (speed) in a different way.
textbooks nis edu kz
plane’s motion during The rate at which an object speeds up, or how fast velocity (speed)
take-off and landing? increases, is called the acceleration. Think of when you get on to a bus
at the bus stop. Its speed increases from zero when the driver presses
the accelerator, and you feel the speed increasing.
The rate at which an object slows down, or how fast your velocity
(speed) decreases, is called the deceleration. Think of when the bus
you got on to now needs to slow down gradually to stop at the traffic
lights. The driver presses the brakes and you feel its speed decreasing.
Therefore, acceleration and deceleration are vector quantities
describing a change of velocity in a unit time.
Let’s just concentrate on acceleration for now, and assume the moving
object has a uniform acceleration – its acceleration is constant. In
mathematical terms, acceleration is the rate of change of the
velocity. This means that the velocity of an object increases by the
same amount in equal intervals of time. The mathematical equation
looks like this:
v–v o
=
t
a – acceleration of an object
v – final velocity at moment in time t
v o – initial velocity at initial moment in time: t o = 0>
m
m
In SI, the unit of acceleration is [ ] = ( / s )/s =
s 2
Deriving from equation (above) velocity of object in accelerated motion
we arrive at:
28 v = v o + a ∙ t
