# Simple kinematic problem

## Homework Statement

An airplane maintains a constant acceleration of 4.0m/s^2 as it speeds up from 16m/s [E] to 28 m/s [E].

A what is the average velocity?

b) how long does the airplane accelerate?

c) when is the instantaneous velocity equal to the average velocity for the interval?

a= 4.0 m/s^2

vi= 16m/s [E]
vf= 28m/s[E]

## The Attempt at a Solution

i found the answer to A and B

Average velocity = 22 m/s. Total time = 3.0 s

I don't know how instantaneous velocity is related to average velocity for the interval. Or how to find the answer. Someone help me?

Last edited:

If you found the average velocity to be 22m/s it is asking when the instantaneous velocity is 22m/s which should just be V = vi + at

Ok got it thanks :)

PeterO
Homework Helper

## Homework Statement

An airplane maintains a constant acceleration of 4.0m/s^2 as it speeds up from 16m/s [E] to 28 m/s [E].

A what is the average velocity?

b) how long does the airplane accelerate?

c) when is the instantaneous velocity equal to the average velocity for the interval?

a= 4.0 m/s^2

vi= 16m/s [E]
vf= 28m/s[E]

## The Attempt at a Solution

i found the answer to A and B

Average velocity = 22 m/s. Total time = 3.0 s

I don't know how instantaneous velocity is related to average velocity for the interval. Or how to find the answer. Someone help me?

When are the two numerically equal?

Suppose you accelerated away from traffic lights for 10 seconds. After 10 seconds you may have reached quite a high speed, but your average speed will be less than that. At some time during the 10 seconds, the speedo will have shown a speed that just happens to equal your average speed [you won't have realised at the time, since you need the full trip to calculate your average speed]. When was that time?

ahh ok thank you so much!

PeterO
Homework Helper

## Homework Statement

An airplane maintains a constant acceleration of 4.0m/s^2 as it speeds up from 16m/s [E] to 28 m/s [E].

A what is the average velocity?

b) how long does the airplane accelerate?

c) when is the instantaneous velocity equal to the average velocity for the interval?

a= 4.0 m/s^2

vi= 16m/s [E]
vf= 28m/s[E]

## The Attempt at a Solution

i found the answer to A and B

Average velocity = 22 m/s. Total time = 3.0 s

I don't know how instantaneous velocity is related to average velocity for the interval. Or how to find the answer. Someone help me?

btw; Part C of this problem is a learning exercise, so that in future you will know the bit I highlighted red.

ok thank you