What does it mean by 'a is constant' in motion..........'?

In summary, motion in a straight line has three formulas (v = u + at, v^2 - u^2 = 2as, and s = ut + 1/2 at^2) that are applicable when acceleration (a) is constant. This means that the acceleration always has a single value and does not vary. However, in the real world, this simplification is rarely seen, as objects like cars and space rockets do not accelerate at a constant rate due to factors like fuel consumption and air resistance. Despite this, it is important to learn and use these formulas as a starting point for understanding motion.
  • #1
HCverma
82
2
Motion in a straight line has three formulas
1. v = u + at
2. v^2 - u^2 = 2as
3. s = ut + 1/2 at^2
These three formulas are applicable when a is constant. Now my question is 'what does it mean by 'when a is constant'? Could you please explain it?
 
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  • #2
It means the acceleration is constant over time.
 
  • #3
HCverma said:
Now my question is 'what does it mean by 'when a is constant'?
About the only 'constant acceleration' situation we encounter is when an object falls from a height of a few tens of metres and when it has a big enough mass that we ignore the effect of air resistance. I must have had my attention elsewhere when those formulae were first presented to me and I spent a lot of time worrying about how that could possibly apply to motor cars accelerating ("Pay attention you little oik!"). It was much later that I actually cottoned on properly.
Cars of course do not accelerate at a constant rate and neither do space rockets because they lose fuel constantly so their mass reduces throughout the burn. But we all need to learn to use those formulae because we have to start somewhere.
 
  • #4
HCverma said:
Now my question is 'what does it mean by 'when a is constant'? Could you please explain it?

It means that the acceleration always has a single value and does not vary. The real world almost never follows this simplification though.
 
  • #5
sophiecentaur said:
Cars of course do not accelerate at a constant rate and neither do space rockets because they lose fuel constantly so their mass reduces throughout the burn.
Or the classic example of an object that often undergoes non-constant acceleration... :biggrin:

https://c8.alamy.com/comp/E5P2E2/a-...h-fighter-aircraft-performs-aerial-E5P2E2.jpg

a-us-air-force-f-22-raptor-stealth-fighter-aircraft-performs-aerial-E5P2E2.jpg
 

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Related to What does it mean by 'a is constant' in motion..........'?

1. What does it mean when we say 'a is constant' in motion?

When we say that 'a is constant' in motion, it means that the acceleration of an object remains the same throughout its motion. This means that there is no change in the rate or direction of the object's velocity, and it is moving at a constant speed.

2. How is 'constant acceleration' different from 'changing acceleration'?

Constant acceleration means that the acceleration of an object remains the same throughout its motion, while changing acceleration means that the object's acceleration is either increasing or decreasing over time. In other words, the rate or direction of the object's velocity is changing.

3. What factors can cause 'a' to be constant in motion?

Several factors can cause 'a' to be constant in motion, such as a constant force acting on the object, a frictionless environment, or a motion in a straight line with no external forces acting on the object.

4. How does 'a is constant' affect an object's motion?

When 'a is constant' in motion, the object will continue to move at a constant speed and in a straight line. This means that the object's velocity will not change, and it will cover equal distances in equal intervals of time.

5. Can 'a' be constant for all types of motion?

No, 'a' cannot be constant for all types of motion. It can only be constant for motion in a straight line. In other types of motion, the acceleration may change due to various factors such as changes in direction, speed, or external forces acting on the object.

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