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December 21, 2014

December 21, 2014

Posted by **Leah** on Wednesday, September 23, 2009 at 6:29pm.

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?

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 6:44pmIt 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.

- Physics but algebra problem -
**Leah**, Wednesday, September 23, 2009 at 6:55pmWhen 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

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 7:27pmRemember 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

- Physics but algebra problem -
**Leah**, Wednesday, September 23, 2009 at 7:35pmProb 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

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 7:42pmLet 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.

- Physics but algebra problem -
**Mia**, Wednesday, September 23, 2009 at 7:53pm260,000 Newtons sorry.

- Physics but algebra problem -
**Leah**, Wednesday, September 23, 2009 at 8:01pmhuh?? 260,000 Newtons?

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 8:03pmMia's post accidently went here. Ignore it.

- Physics but algebra problem -
**Leah**, Wednesday, September 23, 2009 at 8:04pmI'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.

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 8:13pmNo 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

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 8:14pmMy mistake!

stupied = stupid

See, we all make errors.

- Physics but algebra problem -
**James**, Wednesday, September 23, 2009 at 8:23pmSo thats 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.

- Physics but algebra problem -
**Leah**, Wednesday, September 23, 2009 at 8:24pmWhere i am having a problem to....Do you have same prob James? Acceleration is stumping me.

- Physics but algebra problem -
**Quidditch**, Wednesday, September 23, 2009 at 8:31pmGo 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.

- Physics but algebra problem -
**Leah**, Wednesday, September 23, 2009 at 8:39pmThanks so much!!!!

- Physics but algebra problem -
**Anonymous**, Thursday, March 21, 2013 at 12:49pmwhat is the average acceleration of a subway train that slows down from 12 meters/ second to 9.6 meters/ second in 0.8 seconds

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