Solving Physics Problems: A Newbie's Guide

In summary: According to the checker, my answer should be 2747m/s2. However, when I tried to enter that into the internet assignment, I got a negative number. I think I need to do more research on when and how to use dimensional analysis on my internet assignment. In summary, In summary, all objects at the same place on the Earth fall at the same acceleration, which may vary slightly depending on where you are on the surface of the earth, but 9.8 m/sec^2 is a pretty good approximation. As you move away from the centre of the earth, gravity of course falls off as 1/r^2.
  • #1
Chutzpah
7
0
Okay, I am new to physics and for some reason I am not connecting the dots. I would appreciate if a combination of anyone could explain these solutions. I know the 4 kinematics equations but am really unsure if I need to know other things...like the rate at which objects will always fall or rise? Is it always 9.8m/s? Thank you, this is due tomorrow at 8 am. I am new and think this is great. There are 8 simple questions. I really appreciate any help that might be offered.

8. A tennis ball is dropped from 1.36 meters above the ground and rebounds to a height of 0.969 meters.
a. With what velocity does it hit the ground? Hint: Velocity is a vector.
WebAssign will check your answer for the correct number of significant figures. m/s
b. With what velocity does it leave the ground?
WebAssign will check your answer for the correct number of significant figures. m/s
c. If the ball is in contact with the ground for 0.0136 seconds, find the ball's acceleration while touching the ground.
WebAssign will check your answer for the correct number of significant figures. m/s/s

7. During a baseball game, a batter hits a high pop-up. If the ball remains in the air for 6.54 seconds, how high does it rise? Hint: Calculate the height using the second half of the trajectory.

6. A pitcher throws a fastball at a speed of 34.2 meters per second. The acceleration occurs as the pitcher holds the ball in his hand and moves it through an almost straight-line distance of 3.66 meters. Calculate the acceleration, assuming it is uniform. answer is in m/s squared

5. An engineer designs a runway to accommodate airplanes that must reach ground speed of 77.0 meters per second before they can take off. These planes are capable of accelerating uniformly at 2.89 meters per second per second.
a. How long will it take the planes to reach takeoff speed?
WebAssign will check your answer for the correct number of significant figures. s
b. What must be the minimum length of the runway?
WebAssign will check your answer for the correct number of significant figures. m

4. An astronaut drops a feather from 2.21 meters above the surface of the moon. If the acceleration due to gravity is 1.63 meters per second per second down, how long does it take the feather to hit the surface?

3. How far does a plane fly in 24.1 seconds if its velocity is changing uniformly from +160 meters per second to +68 meters per second?

2. Rocket-powered sleds are used to test the responses of humans to acceleration. Starting from rest, a sled can reach a speed of 409 meters per second in 1.99 seconds and can stop again in another 2.32 seconds.
a. Calculate the acceleration of the sled when starting.
WebAssign will check your answer for the correct number of significant figures. wrong check mark m/s/s
b. Calculate the acceleration of the sled when braking.
WebAssign will check your answer for the correct number of significant figures. wrong check mark m/s/s

So far I have attempted a few of these without much success. Thank you again.
 
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  • #2
Chutzpah said:
Okay, I am new to physics and for some reason I am not connecting the dots. I would appreciate if a combination of anyone could explain these solutions. I know the 4 kinematics equations but am really unsure if I need to know other things...like the rate at which objects will always fall or rise? Is it always 9.8m/s? Thank you, this is due tomorrow at 8 am. I am new and think this is great. There are 8 simple questions. I really appreciate any help that might be offered.
All objects at the same place on the Earth fall at the same acceleration. That acceleration may vary slightly depending on where you are on the surface of the earth, but 9.8 m/sec^2 is a pretty good approximation of the acceleration. As you move away from the centre of the earth, gravity of course falls off as 1/r^2.

Why not show us what you have done so we can see where your problems are.

AM
 
  • #3
Well, for number 2 I divided 409 meters per second in 1.99 and 409 by 2.32. In theory, I would think this would give me a negative answer for part 5 since we are braking. According to my internet assignment, these answers are not right. I got a-205.5276382 b--176.2931034 Must I do some dimensional analysis since the answer is in meters per second squared?

In number 3 I used the equation d=vi+vf/2*t, again i am unsure of if and when i need dimensional analysis because for this problem i got 2747m/s2 which is wrong according to the internet checker. Like I said, this is due 8 am tomorrow so any answers would be appreciated. Basically I did d=(160+68)/2*24.1s...right?

I am unsure of when i can use dimensional analysis as well. More to come, but would appreciate any feedback.

At number 4 I used the same equation as above to get 2.712 for time. This is also wrong I guess. My knowns are velocity initial is 1.63 and final is 0(IS this correct?) acceleration is 1.63m/s and distance or displacement is 2.21m. Now I only need to find T. I plug in the equation and get 2.712 rounded which according to mr computer is not right. There has to be something universal i am justn ot seeing or doing wrong.

For number 5 I sued the equation vfsquared=vinitialsquared+2ad. Plugged this into get 5929+0=5.78d which gave me 1025.779 which would gave me the runway length which according to mr computer once again is wrong. To find time I divided 77 by 2.89 to get 26.644 which is the number of seconds it takes to get to top speed. Why are these wrong?
 
Last edited:
  • #4
Chutzpah said:
Well, for number 2 I divided 409 meters per second in 1.99 and 409 by 2.32. In theory, I would think this would give me a negative answer for part 5 since we are braking. According to my internet assignment, these answers are not right. I got a-205.5276382 b--176.2931034 Must I do some dimensional analysis since the answer is in meters per second squared?
What about significant figures? The answers should be 206 and -176 m/sec^2.

In number 3 I used the equation d=vi+vf/2*t, again i am unsure of if and when i need dimensional analysis because for this problem i got 2747m/s2 which is wrong according to the internet checker. Like I said, this is due 8 am tomorrow so any answers would be appreciated. Basically I did d=(160+68)/2*24.1s...right?
t is in the numerator:

[tex]d = v_{avg}\Delta t = \frac{v_i + v_f}{2}\Delta t[/tex]

Make sure you get the sig. figs. right.

AM
 
  • #5
Hello everyone!
I am hoping that you could help me with this one:
A shaft 15 cm in diameter is to b turned on a lathe which has a linear speed of 180m/min, wat is its angular speed? Would I be correct If I use w=v/r to compute for its angular speed? Plsssssss help. I need this badly...:confused:
 

FAQ: Solving Physics Problems: A Newbie's Guide

1. How can I improve my problem-solving skills in physics?

To improve your problem-solving skills in physics, it is important to understand the fundamental concepts and principles of the subject. Start by reviewing the basic equations and laws of physics, and then practice solving problems using these equations. It is also helpful to work through different types of problems and to seek help from a teacher or tutor if you are struggling with a specific concept or technique.

2. What are some common mistakes to avoid when solving physics problems?

One common mistake students make when solving physics problems is using incorrect units or forgetting to convert units. Another mistake is not drawing clear and accurate diagrams to represent the problem. It is also important to be careful with mathematical calculations and to double-check your work for any errors. Finally, make sure to read the problem carefully and understand what is being asked before attempting to solve it.

3. How can I approach a physics problem if I don't know where to start?

If you are unsure of how to start solving a physics problem, it can be helpful to break it down into smaller, more manageable parts. Start by identifying the known and unknown variables and think about which equations or principles can be used to relate them. You can also try working backwards from the answer and see if you can figure out the steps needed to get there. Don't be afraid to ask for help or consult a textbook or online resources for guidance.

4. What are some strategies for solving complex physics problems?

One strategy for solving complex physics problems is to break them down into smaller, simpler problems. You can also try working backwards from the final answer or using trial and error to test different approaches. Another helpful strategy is to draw clear and accurate diagrams to visualize the problem and identify key variables. Practice and perseverance are also key in tackling complex physics problems.

5. How can I check my answer to a physics problem to make sure it is correct?

To check your answer to a physics problem, you can use the units and significant figures to make sure they are consistent with the given information. You can also plug your answer back into the original equation to see if it satisfies all the given conditions. If possible, try to solve the problem using a different method or approach to see if you get the same answer. Finally, it is always a good idea to have someone else check your work or to compare your answer with a solution key or answer guide.

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