Question

For what kind of motion are the instantaneous and average velocities equal?

Why is the answer constant-velocity motion?

Answer 1

@dan815
@UnkleRhaukus
can you please help me?

Answer 2

@DanJS

Answer 3

because there is no acceleration when an object is moving with constant velocity so the instantaneous velocity is constant. If velocity isn't changing, the average over any interval is equal to the velocity at any specific time.

Answer 4

then is it possible for an object's acceleration to be zero if the velocity if zero

Answer 5

@Zale101

Answer 6

You can't confidently say that if acceleration is zero then velocity will surely be zero or if velocity is zero then acceleration will surely be zero. Like suppose a car is moving with a constant velocity then it's in uniform motion i.e. it has a velocity but no acceleration also think what happens when we throw a ball vertically above the ground, at a instant after attaining certain height its velocity becomes zero but it is still experiencing an acceleration (acceleration due to gravity) towards the ground so a body can have a zero velocity but still be accelerated.

Answer 7

ok. how can you determine the speed of an object with the acceleration

Answer 8

\(\color{blue}{\text{Originally Posted by}}\) @prguan
For what kind of motion are the instantaneous and average velocities equal?

Why is the answer constant-velocity motion?
\(\color{blue}{\text{End of Quote}}\)

Suppose a car is moving with an accelerated motion such that its acceleration is \(\sf 1 m/s^2\). Now let's note its velocity at different instants.

Time Velocity
0 0
1 1
2 2
3 3


We see that its instant velocity at different instants of time will be different like, 1, 2 and \(\sf 3 m/s\) but its average velocity will be 3m/s \(\sf (\frac{1+2+3}{3})\)

Answer 9

why is the average velocity 3m/s
(1+2+3)=6
6/3 is 2

Answer 10

No I am sorry, average velocity will be equal to

\(\sf \frac{Total~Distance}{Total~Time}\)

And in the above case total distance = \(\sf (1 \times 1) +(1\times 2)+(1\times 3)\)

Total time = 3 seconds, so average velocity = 2m/s

Answer 11

Now, let's consider the case of a car going through a constant velocity of say 3 m/s i.e. it has no acceleration. Right?

Let's do the same experiment and note its velocities at various instants of time.


Time Velocity
0 0
1 3
2 3
3 3

So we see that velocity this car is same at all the instant of times and not only that its average velocity is also same as its instantaneous velocity. Check this by finding out its average velocity as i did in the above table.

Answer 12

oh ok
i though to find acceleration it was
distance/ time

Answer 13

No, Distance/Time = Velocity and this formula is only applicable when the object is moving with constant velocity i.e. it has zero acceleration.

To find acceleration you can use formula,

V=U+at, where,

V= final velocity
U= initial velocity
a= acceleration
t=time

Answer 14

so
final velocity= initial velocity + acceleration x time x where
is where- displacement

Answer 15

what does where represent?

Answer 16

No where is nothing c:

Answer 17

im confused

Answer 18

No, Distance/Time = Velocity and this formula is only applicable when the object is moving with constant velocity i.e. it has zero acceleration.

To find acceleration you can use formula,

\(\boxed{V=U+at}\)

Where, the symbols has following meaning
V= final velocity
U= initial velocity
a= acceleration
t=time

Answer 19

Is it clear now?

Answer 20

i guess