Motion: Solving problems using equations

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In summary, the question is about calculating the distance and time for a 100m sprint, with an initial acceleration from rest for 3.5 seconds at 2.8 m/s (squared). The equation used is d= v1t + 1/2a t (squared), with the initial speed being 0 m/s. The correct answer is 17 m.
  • #1
tryintosurviv
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Im sorry if this is in the wrong area ! and I know that this is the easiest question in the history of physics but I need help. I think some of the answers in the back of the text are wrong but I might be just the biggest idiot on the face of the Earth so feel free to point that out. anyways ...

Homework Statement


If 100m sprinters accelerate from rest for 3.5 s at 2.8 m/s (squared) , how far have they ran to this point ? How long will it take them to complete the 100m sprint , assuming they maintain their speed the rest of the way ?

Homework Equations



d= v1t + 1/2a t (squared)

I think ?

The Attempt at a Solution



= 3.5 + 1/2 (2.8)(3.5) squared
= 3.5 + 1/2 (2.8)(12.3)
=3.5 + 34.2 divided by 2
= 3.5 + 17.2
= 20.7 sorry I don't have the division sign or superscript

and I can't do the rest of the question without having the first answer correct. The text says the answer is 17 m


HELP ! Please help a huge idiot
 
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  • #2
Hint: What's the initial speed? (What you call v1.)
 
  • #3
Isn't it 0 m/s ? It says from rest
 
  • #4
tryintosurviv said:
Isn't it 0 m/s ? It says from rest
Exactly! Do you see what's wrong with your calculation now?
 
  • #5
OH wow that's great. I was adding instead of multiplying ! Thanks
 

FAQ: Motion: Solving problems using equations

1. What is motion?

Motion is the change in position of an object over time. It can be described using concepts such as velocity, acceleration, and displacement.

2. How do you solve problems involving motion using equations?

To solve problems involving motion, you can use equations such as the equations of motion (v = u + at, s = ut + 1/2at^2, and v^2 = u^2 + 2as) or the kinematic equations (v = u + at, s = ut + 1/2at^2, v = u + 1/2at, and s = 1/2(u + v)t).

3. What are the most common equations used to solve motion problems?

The most common equations used to solve motion problems are the equations of motion, which relate an object's initial and final velocity, acceleration, and displacement, and the kinematic equations, which relate an object's displacement, velocity, and acceleration over time.

4. How do you know which equation to use for a specific motion problem?

The equation you use will depend on the given information in the problem. If you are given an object's initial and final velocity, acceleration, and/or displacement, you can use the equations of motion. If you are given an object's displacement, velocity, and/or acceleration over time, you can use the kinematic equations.

5. Can motion problems be solved without using equations?

Yes, motion problems can also be solved using graphical methods, such as drawing a velocity-time or position-time graph and analyzing the slope or area under the curve. However, using equations can provide a more precise and efficient method of solving motion problems.

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