Physics but algebra problem
posted by Leah on .
Having issue with algebra.
89N=ma
99N=m2a
would you do something like plugging one into the other such as.
a=89/m
99N=99/(2(89/m)
prob is when i get a fraction in the denominator i get confused can someone help me. I'm trying to find the mass. Which i will then convert into weight (N). N=mg.
Can someone help?

It doesn't look like there is a solution.
First equation:
89N = ma
Second equation:
99N = m2a
For the second equation, if you divide both sides by 2 you get:
99N/2 = m2a/2
49.5N = ma
The first equation says ma = 89N.
The second equation says ma = 49.5N
Assuming a is constant, there is no single value of m that satisfies both equations. 
When you lift a bowling ball with a force of 89 , the ball accelerates upward with an acceleration . If you lift with a force of 99 , the ball's acceleration is 2.
I'm guessing a is 9.8 m/s since it's gravity.
I trying to figure out the weight w and acceleration a.
w=mg
a=F/m 
Remember that the acceleration of the bowling ball is the NET force of your lifting and gravity.
So, the acceleration of your 89N lifting is:
a = (89N  mg)/m
where g is gravity.
Likewise for the 99N lift:
a = (99N  mg)/m 
Prob is I not sure exactly how to do the algebra when I plug in the a. and doesn't the m just cancel out? 0_0

Let a = the acceleration for 89N
Let m = the bowling balls mass.
Let g = acceleration of gravity.
So, 2a is the acceleration for 99N.
Set up the equation that shows the 99N acceleration is 2 times the 89N acceleration:
2(89N  mg)/m = (99N  mg)/m
Solve for m. 
260,000 Newtons sorry.

huh?? 260,000 Newtons?

Mia's post accidently went here. Ignore it.

I'm not sure how to do the algebra the m in the denominator is confusing me. 0_0 so sorry i'm so difficult i feel stupid. not sure how to solve for m.

No problem. That is why we are here. You are not being difficult or stupied at all. No one is born knowing this stuff.
Some more hints:
2(89N  mg)/m = (99N mg)/m
Let's get rid of the denominator.
Multiply both sides by m to get:
2(89N  mg) = (99N  mg)
Multiplying out the left side:
178N  2mg = 99N  mg
Add 2mg to both sides:
178N = 99N + mg
Subtract 99N from both sides:
79N = mg
So,
m = 79N/g 
My mistake!
stupied = stupid
See, we all make errors. 
So that's what i got buttt for some reason the acceleration doesn't match up for the mass i'm getting from it. Why I am having such a difficult problem. See when I do N=mg i am getting m=79/9.81. Prob is for acceleration for both those forces the equation N=mg isn't working so it's confusing me.

Where i am having a problem to....Do you have same prob James? Acceleration is stumping me.

Go back and look at the two acceleration equations posted above. Don't forget to include gravity.
for 89N:
a = (89N  mg)/m
m and g are known
for 99N;
a = (99 mg)/m
The acceleration at 99N should be twice the 89N a. 
Thanks so much!!!!

what is the average acceleration of a subway train that slows down from 12 meters/ second to 9.6 meters/ second in 0.8 seconds