Is the ADA's Sample Physics Problem Incorrect?

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In summary, the sample physics problem given by the ADA on their website is wrong. Can anyone confirm? It says: A ball is thrown horizontally at 20 m/s from the top of a building and strikes level ground 50 m from the building. How high is the building? When I solve this, I get 62m, but the answer is 31m. I assume the discrepancy is the horizontal velocity. I'm assuming it is constant while maybe it should be an average? Can anyone help me confirm this? I thought I had a strong hold on kinematics and I'm worried I'm getting stuck on this problem.
  • #1
burapi
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Hi, I think the sample physics problem given by the ADA on their website is wrong. Can anyone confirm? It says: A ball is thrown horizontally at 20 m/s from the top of a building and strikes level ground 50 m from the building. How high is the building?

When I solve this, I get 62m, but the answer is 31m. I assume the discrepancy is the horizontal velocity. I'm assuming it is constant while maybe it should be an average? Can anyone help me confirm this? I thought I had a strong hold on kinematics and I'm worried I'm getting stuck on this problem.

Thank you, anyone!
 
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  • #2
burapi said:
Hi, I think the sample physics problem given by the ADA on their website is wrong. Can anyone confirm? It says: A ball is thrown horizontally at 20 m/s from the top of a building and strikes level ground 50 m from the building. How high is the building?

When I solve this, I get 62m, but the answer is 31m. I assume the discrepancy is the horizontal velocity. I'm assuming it is constant while maybe it should be an average? Can anyone help me confirm this? I thought I had a strong hold on kinematics and I'm worried I'm getting stuck on this problem.

Thank you, anyone!

The answer on the website is correct, and the horizontal velocity is meant to be constant. It seems you do not use the correct equation.
 
  • #3
The time of flight, assuming contant horizontal velocity, is:

t = 50m/(20 m/s) = 2.5s.

Using s = u*t + 0.5 * a * t^2 you get 31 m.

Getting 62m looks like you forgot the 0.5.
 
  • #4
My guess is you used the vertical velocity at impact instead of the average vertical velocity...
 
  • #5
Yes, thank you for pointing out I used the wrong equation. I did indeed leave out the 1/2. Ironically I am relieved and can move on!

You guys are so great :)
 

Related to Is the ADA's Sample Physics Problem Incorrect?

1. Is it possible for a test question to be wrong?

Yes, it is possible for a test question to be wrong. Test questions are created by humans and can contain errors or be unclear in their wording. It is important for educators to carefully review and test their questions before administering them to students.

2. How do I know if a test question is wrong?

If you are unsure about the accuracy of a test question, you can consult with your teacher or professor. They can provide clarification and explain the reasoning behind the question if necessary. You can also compare your answer to the answer key or discuss it with your classmates.

3. What should I do if I believe a test question is wrong?

If you believe a test question is wrong, you can bring it to the attention of your teacher or professor. They may review the question and make any necessary corrections, or provide an explanation for why the question is not wrong. It is important to discuss your concerns respectfully and provide evidence for your argument.

4. Can a test question be subjective and therefore not technically wrong?

Yes, some test questions may be subjective and not have a clear right or wrong answer. These types of questions often require students to provide their own analysis or opinions. However, it is still important for these questions to be fair and unbiased in their wording and content.

5. Should I challenge a test question if I think it is wrong?

If you strongly believe a test question is wrong and can provide evidence to support your argument, it is appropriate to challenge the question. However, it is important to do so respectfully and to be open to the possibility that you may be mistaken. It is also important to follow the proper channels and discuss your concerns with your teacher or professor before approaching higher authorities.

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