Instantaneous velocity

  • #1
6
0

Homework Statement


Is it possible for the instantaneous velocity of an object at some time, t1, to not be parallel to the average velocity over a short time interval, Δt=t2-t1? If it is not possible, explain why not. If it is possible, explain what this situation implies about the motion of the object.

Homework Equations




The Attempt at a Solution


i would say it's possible when acceleration is zero but I'm not sure
 

Answers and Replies

  • #2
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,435
3,499

Homework Statement


Is it possible for the instantaneous velocity of an object at some time, t1, to not be parallel to the average velocity over a short time interval, Δt=t2-t1? If it is not possible, explain why not. If it is possible, explain what this situation implies about the motion of the object.

Homework Equations




The Attempt at a Solution


i would say it's possible when acceleration is zero but I'm not sure

Are you saying that it is possible for the instantaneous velocity to not be parallel to the average velocity when the acceleration is zero?
 
  • #3
6
0
Are you saying that it is possible for the instantaneous velocity to not be parallel to the average velocity when the acceleration is zero?
yes but I'm not sure
 
  • #4
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,435
3,499
yes but I'm not sure
OK, let's make sure you're sure. Please answer the following questions
1. What do you need to do to find the average velocity, i.e. what is an expression that will allow you to calculate it?
2. If an object has initial velocity v1 to the right at time t1 and its acceleration is zero, how will its velocity change at some later time t2?
3. Given (1) and (2) above, what is the average velocity of this object from time t1 to time t2?
 
  • #5
6
0
OK, let's make sure you're sure. Please answer the following questions
1. What do you need to do to find the average velocity, i.e. what is an expression that will allow you to calculate it?
2. If an object has initial velocity v1 to the right at time t1 and its acceleration is zero, how will its velocity change at some later time t2?
3. Given (1) and (2) above, what is the average velocity of this object from time t1 to time t2?
1) Δf/Δt
2)The velocity won't change because the acceleration which is the change in velocity is zero
3)i don't know how i can get this without the velocity and time
 
  • #6
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,435
3,499
Two points for your answer in 1. (a) Velocity is a vector and so is average velocity. You don't show a vector equation; (b) What is the meaning of f in Δf/Δt?
Your answer in 2 is correct.
For 3 think again. If the velocity is v1 to the right at t1 and it doesn't change, what could it be at time t2?
 
  • #7
6
0
Two points for your answer in 1. (a) Velocity is a vector and so is average velocity. You don't show a vector equation; (b) What is the meaning of f in Δf/Δt?
Your answer in 2 is correct.
For 3 think again. If the velocity is v1 to the right at t1 and it doesn't change, what could it be at time t2?
velocity at t2 would still be the same if it does not change
 
  • #8
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,435
3,499
velocity at t2 would still be the same if it does not change
Good. Now how do you think the instantaneous velocity compares with the average velocity when the acceleration is zero? If the two are the same, why are they? If they are different, in what way?
 
  • #9
6
0
It's going to be the same because there is no change in acceleration
 
  • #10
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,435
3,499
It's going to be the same because there is no change in acceleration
That's not the reason. When the acceleration is zero, the average velocity is the same as the instantaneous velocity because something other than the acceleration is not changing. What is that?
 
  • #11
6
0
That's not the reason. When the acceleration is zero, the average velocity is the same as the instantaneous velocity because something other than the acceleration is not changing. What is that?
Velocity?
 
  • #12
kuruman
Science Advisor
Homework Helper
Insights Author
Gold Member
10,435
3,499
Are you asking me or are you telling me? See your answer 2 in post #5. OK, so we have found that, when the acceleration is zero, the instantaneous velocity vector is the same as the average velocity vector. Now answer this, what must be true for two vectors to be the same?
 

Related Threads on Instantaneous velocity

Replies
1
Views
352
Replies
6
Views
34K
Replies
4
Views
43K
  • Last Post
Replies
4
Views
1K
Replies
3
Views
449
Replies
1
Views
9K
  • Last Post
Replies
4
Views
10K
  • Last Post
Replies
7
Views
578
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
2
Views
1K
Top