Is Motion Always Positive or Negative in Physics Problems?

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SUMMARY

The discussion clarifies the concepts of motion in physics, specifically regarding acceleration, velocity, and displacement. For a ball thrown upward, it experiences positive acceleration, negative velocity, and positive displacement. Conversely, when a ball falls, it has negative acceleration, positive velocity, and negative displacement. In the case of a car, moving forward while braking results in negative acceleration and negative velocity, while moving backward and accelerating also yields negative velocity and negative acceleration. The signs of displacement align with those of velocity in these scenarios.

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  • Understanding of basic physics concepts such as acceleration, velocity, and displacement.
  • Familiarity with the principles of motion in one dimension.
  • Knowledge of how to interpret signs (positive and negative) in physics equations.
  • Ability to analyze motion scenarios involving different directions and speeds.
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Students studying physics, educators teaching motion concepts, and anyone interested in understanding the dynamics of acceleration, velocity, and displacement in real-world scenarios.

willingtolearn
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Homework Statement
#1
a) A ball is throwing straight upward, Is that motion positive or negative acceleration/velocity/displacement ?
b) A ball is falling down (what go up must come down), Is that a positive or negative acceleration/velocity/displacement ?

#2
a) A car is moving forward then the driver step on brake, Is that motion positive or negative acceleration/velocity ?
b) A car is moving backward then the driver step on brake, Is that motion positive or negative acceleration/velocity/displacement ?
c)A car is moving backward then the driver step on gas, Is that motion positive or negative acceleration/velocity/displacement ?

My answers
#1
a) positive acceleration, negative velocity (the velocity is decreasing), positive displacement
b) negative acceleration, positive velocity (the velocity is increasing), negative displacement
#2
a) negative acceleration (the car is slowing down), negative velocity,
b) same a
c) i got confused
 
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careful... positive velocity just means it is moving foward or upward... negative velocity just means it is moving backwards or downwards... it doesn't meant that the speed is decreasing (that gives information about acceleration).

If an object is moving forward and slowing down... that means velocity is positive and acceleration is negative. Also, if an object is moving backwards and speeding up backwards... acceleration is again negative.

Give these another shot.
 
Last edited:
#1
a)positive velocity, negative acc
b)negative velocity, negative acc
#2
a)positive velocity, negative acc
b)negative velocity, positive acc
c)negative velocity, negative acc
Is those right ?
 
willingtolearn said:
#1
a)positive velocity, negative acc
b)negative velocity, negative acc
#2
a)positive velocity, negative acc
b)negative velocity, positive acc
c)negative velocity, negative acc
Is those right ?

All correct! But you didn't write the displacements.
 
oh i forgot, Is the sign of displacements the same with velocity ? positive - up, back
negative back and down
 
willingtolearn said:
oh i forgot, Is the sign of displacements the same with velocity ? positive - up, back
negative back and down

Yes, in these cases it is.
 

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