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when the equation of position is negative its derivative is positive which is velocity which confuses me
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there is something that doesn't make sense to me
i know that Velocity is the derivative of position fine
now when i differentiate D = T^3 i get the equation of velocity is 3T^2 which is completely okay until T is negative if t is -3
then position is -27 and velocity is 18 which is logically wrong
calculus derivatives mathematical-physics
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
asked Aug 5 at 23:56
Nour Ahmed
31
 |Â
show 5 more comments
up vote
-1
down vote
favorite
there is something that doesn't make sense to me
i know that Velocity is the derivative of position fine
now when i differentiate D = T^3 i get the equation of velocity is 3T^2 which is completely okay until T is negative if t is -3
then position is -27 and velocity is 18 which is logically wrong
calculus derivatives mathematical-physics
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
asked Aug 5 at 23:56
Nour Ahmed
31
1
Why do you think it is logically wrong?
– caverac
Aug 5 at 23:59
You really need to look at velocity as the rate of change in position. You can be anywhere, negative or positive, and be moving in the positive direction.
– Carser
Aug 5 at 23:59
1
First, you should ask yourself why you think that sounds wrong. What does a negative position have anything to do with velocity? Let us think of an example... we have our house at the origin, and lets call "east" the positive direction. We have a friend who is running east at a constant rate and begins west of our house. So... he's running, and running, and eventually passes our house and keeps running east. His velocity in this example is positive (i.e. is running east) at all times, including when he is currently west of the house as well as when he is eventually east of the house.
– JMoravitz
Aug 5 at 23:59
because if i am moving with 18 m/s then i should be moving forward while indeed i am moving backward
– Nour Ahmed
Aug 6 at 0:00
@JMoravitz but if he is moving on the opposite direction of the house then he should have his velocity negative he moving on the negative direction
– Nour Ahmed
Aug 6 at 0:02
 |Â
show 5 more comments
up vote
-1
down vote
favorite
up vote
-1
down vote
favorite
there is something that doesn't make sense to me
i know that Velocity is the derivative of position fine
now when i differentiate D = T^3 i get the equation of velocity is 3T^2 which is completely okay until T is negative if t is -3
then position is -27 and velocity is 18 which is logically wrong
calculus derivatives mathematical-physics
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
asked Aug 5 at 23:56
Nour Ahmed
31
there is something that doesn't make sense to me
i know that Velocity is the derivative of position fine
now when i differentiate D = T^3 i get the equation of velocity is 3T^2 which is completely okay until T is negative if t is -3
then position is -27 and velocity is 18 which is logically wrong
calculus derivatives mathematical-physics
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
asked Aug 5 at 23:56
Nour Ahmed
31
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
edited Aug 6 at 0:11
Ethan Bolker
35.8k54299
35.8k54299
asked Aug 5 at 23:56
Nour Ahmed
31
asked Aug 5 at 23:56
Nour Ahmed
31
asked Aug 5 at 23:56
Nour Ahmed
31
31
1
Why do you think it is logically wrong?
– caverac
Aug 5 at 23:59
You really need to look at velocity as the rate of change in position. You can be anywhere, negative or positive, and be moving in the positive direction.
– Carser
Aug 5 at 23:59
1
First, you should ask yourself why you think that sounds wrong. What does a negative position have anything to do with velocity? Let us think of an example... we have our house at the origin, and lets call "east" the positive direction. We have a friend who is running east at a constant rate and begins west of our house. So... he's running, and running, and eventually passes our house and keeps running east. His velocity in this example is positive (i.e. is running east) at all times, including when he is currently west of the house as well as when he is eventually east of the house.
– JMoravitz
Aug 5 at 23:59
because if i am moving with 18 m/s then i should be moving forward while indeed i am moving backward
– Nour Ahmed
Aug 6 at 0:00
@JMoravitz but if he is moving on the opposite direction of the house then he should have his velocity negative he moving on the negative direction
– Nour Ahmed
Aug 6 at 0:02
 |Â
show 5 more comments
1
Why do you think it is logically wrong?
– caverac
Aug 5 at 23:59
You really need to look at velocity as the rate of change in position. You can be anywhere, negative or positive, and be moving in the positive direction.
– Carser
Aug 5 at 23:59
1
First, you should ask yourself why you think that sounds wrong. What does a negative position have anything to do with velocity? Let us think of an example... we have our house at the origin, and lets call "east" the positive direction. We have a friend who is running east at a constant rate and begins west of our house. So... he's running, and running, and eventually passes our house and keeps running east. His velocity in this example is positive (i.e. is running east) at all times, including when he is currently west of the house as well as when he is eventually east of the house.
– JMoravitz
Aug 5 at 23:59
because if i am moving with 18 m/s then i should be moving forward while indeed i am moving backward
– Nour Ahmed
Aug 6 at 0:00
@JMoravitz but if he is moving on the opposite direction of the house then he should have his velocity negative he moving on the negative direction
– Nour Ahmed
Aug 6 at 0:02
1
1
Why do you think it is logically wrong?
– caverac
Aug 5 at 23:59
Why do you think it is logically wrong?
– caverac
Aug 5 at 23:59
You really need to look at velocity as the rate of change in position. You can be anywhere, negative or positive, and be moving in the positive direction.
– Carser
Aug 5 at 23:59
You really need to look at velocity as the rate of change in position. You can be anywhere, negative or positive, and be moving in the positive direction.
– Carser
Aug 5 at 23:59
1
1
First, you should ask yourself why you think that sounds wrong. What does a negative position have anything to do with velocity? Let us think of an example... we have our house at the origin, and lets call "east" the positive direction. We have a friend who is running east at a constant rate and begins west of our house. So... he's running, and running, and eventually passes our house and keeps running east. His velocity in this example is positive (i.e. is running east) at all times, including when he is currently west of the house as well as when he is eventually east of the house.
– JMoravitz
Aug 5 at 23:59
First, you should ask yourself why you think that sounds wrong. What does a negative position have anything to do with velocity? Let us think of an example... we have our house at the origin, and lets call "east" the positive direction. We have a friend who is running east at a constant rate and begins west of our house. So... he's running, and running, and eventually passes our house and keeps running east. His velocity in this example is positive (i.e. is running east) at all times, including when he is currently west of the house as well as when he is eventually east of the house.
– JMoravitz
Aug 5 at 23:59
because if i am moving with 18 m/s then i should be moving forward while indeed i am moving backward
– Nour Ahmed
Aug 6 at 0:00
because if i am moving with 18 m/s then i should be moving forward while indeed i am moving backward
– Nour Ahmed
Aug 6 at 0:00
@JMoravitz but if he is moving on the opposite direction of the house then he should have his velocity negative he moving on the negative direction
– Nour Ahmed
Aug 6 at 0:02
@JMoravitz but if he is moving on the opposite direction of the house then he should have his velocity negative he moving on the negative direction
– Nour Ahmed
Aug 6 at 0:02
 |Â
show 5 more comments
1 Answer
1
active
oldest
votes
up vote
0
down vote
accepted
Suppose you are moving to the right but you are still on the left side of a reference point which we call it $0$
As long as you are on the left side of zero the position is negative and as long as you are moving to the right your velocity is positive.
You may as well get to the right side of the reference point and start moving to the left, which means your position is positive and your velocity is negative.
There is not confusion about it.
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
add a comment |Â
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
accepted
Suppose you are moving to the right but you are still on the left side of a reference point which we call it $0$
As long as you are on the left side of zero the position is negative and as long as you are moving to the right your velocity is positive.
You may as well get to the right side of the reference point and start moving to the left, which means your position is positive and your velocity is negative.
There is not confusion about it.
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
add a comment |Â
up vote
0
down vote
accepted
Suppose you are moving to the right but you are still on the left side of a reference point which we call it $0$
As long as you are on the left side of zero the position is negative and as long as you are moving to the right your velocity is positive.
You may as well get to the right side of the reference point and start moving to the left, which means your position is positive and your velocity is negative.
There is not confusion about it.
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
add a comment |Â
up vote
0
down vote
accepted
up vote
0
down vote
accepted
Suppose you are moving to the right but you are still on the left side of a reference point which we call it $0$
As long as you are on the left side of zero the position is negative and as long as you are moving to the right your velocity is positive.
You may as well get to the right side of the reference point and start moving to the left, which means your position is positive and your velocity is negative.
There is not confusion about it.
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
Suppose you are moving to the right but you are still on the left side of a reference point which we call it $0$
As long as you are on the left side of zero the position is negative and as long as you are moving to the right your velocity is positive.
You may as well get to the right side of the reference point and start moving to the left, which means your position is positive and your velocity is negative.
There is not confusion about it.
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
answered Aug 6 at 0:25
Mohammad Riazi-Kermani
27.8k41852
27.8k41852
add a comment |Â
add a comment |Â
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1
Why do you think it is logically wrong?
– caverac
Aug 5 at 23:59
You really need to look at velocity as the rate of change in position. You can be anywhere, negative or positive, and be moving in the positive direction.
– Carser
Aug 5 at 23:59
1
First, you should ask yourself why you think that sounds wrong. What does a negative position have anything to do with velocity? Let us think of an example... we have our house at the origin, and lets call "east" the positive direction. We have a friend who is running east at a constant rate and begins west of our house. So... he's running, and running, and eventually passes our house and keeps running east. His velocity in this example is positive (i.e. is running east) at all times, including when he is currently west of the house as well as when he is eventually east of the house.
– JMoravitz
Aug 5 at 23:59
because if i am moving with 18 m/s then i should be moving forward while indeed i am moving backward
– Nour Ahmed
Aug 6 at 0:00
@JMoravitz but if he is moving on the opposite direction of the house then he should have his velocity negative he moving on the negative direction
– Nour Ahmed
Aug 6 at 0:02