SUVAT Problems: Why t-x and Not t+x?

In summary, when solving SUVAT problems, the item that begins motion later is given a time "t-x" where x>0, rather than t+x. This is because the SUVAT formula only works if the object is stationary at t = 0. Each object has its own clock, so the first object starts at t1 = 0 and the second object starts at t2 = 0, which is when t1 = 5. Therefore, t2 = t1 - 5.
  • #1
When doing SUVAT problems, why does the item which begins motion later given a time "t-x" where x>0. For example, if dropping a ball, and then dropping another ball 5 seconds later, the first ball's time can be expressed as "t" and the second ball's time as "t-5". Why is it not t+5?

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  • #2
Hi nokia8650! :smile:

Because the SUVAT formula you're using (I assume) only works if the ball is stationary at t = 0.

Imagine each ball has its own clock, the first showing t1 and the second showing t2.

So t1 = 0 when the first ball starts.

And t2 = 0 when the second ball starts, which of course is when t1 = 5.

So t2 = t1 - 5. :smile:
  • #3
Thanks alot!

1. Why do we use t-x instead of t+x in SUVAT problems?

The t-x notation in SUVAT problems is used to represent the displacement or change in position of an object, while t+x represents the final position of the object. This notation is used because it is easier to calculate and understand the change in position rather than the final position, as it takes into account the initial position of the object.

2. Can we use t+x instead of t-x in SUVAT problems?

Technically, yes, we can use t+x instead of t-x in SUVAT problems. However, the t-x notation is the standard convention and is more commonly used in physics and mathematics. It is important to stick to this convention for consistency and clarity when solving SUVAT problems.

3. What does the "t" in t-x stand for?

The "t" in t-x stands for time. In SUVAT problems, time is an important variable as it represents the duration of the motion or the change in position of an object. The t-x notation helps to indicate that time is involved in the equation.

4. Are there any other notations used in SUVAT problems?

Yes, apart from t-x, there are three other notations used in SUVAT problems: s-x, u-x, and v-x. These notations represent displacement, initial velocity, and final velocity, respectively. All four notations are interconnected and are used to solve various kinematic problems involving motion.

5. How do I know when to use t-x in SUVAT problems?

The t-x notation is used when solving kinematic problems that involve calculating the displacement or change in position of an object. If the problem involves finding the final position or any of the other variables, a different notation will be used. It is important to carefully read and understand the problem to determine which notation to use.