Search: To find out answers to a specific question, copy a representative sentence from the question and paste the sentence in the search form and search it. The results show the most related questions and yours may be in there. Feel free to share LeiAcademy.org with other teachers and students.  
To discourage spam, only registered users can ask questions.

Welcome to Physics Homework and Study Help, where you can ask questions and receive help on learning physics. We currently focus on helping questions in introductory level college physics and high school AP Physics courses.
To discourage spam, only registered users can ask questions.

Facebook Twitter Google

Welcome to Physics Homework Help Page on LeiAcademy.org

Feel free to ask a question and also answer questions others asked. Answering others' questions can in turn help one's own understanding and build a warm healthy community for learning. The followings list a few things that might be helpful for you to effectively obtain help on specific physics homework or practice problems.  

Search: To find out answers to a specific questions, copy a representative sentence from the question and paste the whole sentence in the search form and search it. The results will show the most related questions and yours may be in there

Browse: To find out what have been discussed, asked or answered, put in a few key words in the search form and search for related questions, answers, and or solutions. Or you can click the related tags or other tabs to find useful information there. 

You can also write professional-looking equations using Latex codes (see details here).

This site is hosted on LeiAcademy.org, which will continue to add new resources for learning. Feel free to share this with other teachers and students.  

Two acceleration questions. Need answers with deductions!

0 votes
47 views
1. A body on a straight road with constant acceleration takes a 10 meter long track in 1,06 sec, and the next 10 m track in 2,2 sec. What is the acceleration?

2. A plane with constant acceleration until the half of the runway reaches the 80% of the velocity required for the take off.
What fractional part of the track does it reach the take-off speed?
asked Nov 17, 2014 in Highschool Physics by Erin (120 points)

1 Answer

0 votes
1) You want to first find the average velocity during each segment. These average velocities are the the instantaneous velocities when the time is halfway through a segment ( 0.53 sec for v1, and 1.1 sec for v2). Using these we can find the acceleration:

$$d_1 = v_1 t_1$$
$$d_2=v_2 t_2$$
$$a = 2\frac{v_2-v_1}{t_2+t_1}$$

*Note that the 2 comes from the fact we want only HALF the time in each segment.

Being that the second segment takes longer than the first segment, you should expect your answer to be negative.

 

2) Assuming the acceleration is constant the entire time:

$$ v_f^2=v_0^2+2a(x_f-x_0)$$

Simplifies to

$$ (\frac{4}{5} v)^2 = 2a(\frac{1}{2}d)$$

which we can compare to an equation for the FULL take-off speed:

$$v^2 = 2a x_{takeoff}$$

The two equations can then be divided leaving

$$\frac{25}{16}= \frac{x_{takeoff}}{0.5 d}$$

Which results in

$$x_{takeoff}= \frac{ 25}{32} d$$
answered Nov 17, 2014 by jcf1559 (2,140 points)
edited Nov 17, 2014 by jcf1559
Is this site is not working . As for a long time no question has been answered .
web counter
...