Calculating Force with Mass and Acceleration

[socialfox]

Homework Statement

Mass= 36.1 (Grams)
Acceleration = 1.36 M/S(sqaured)
Net Force in MiliNewtons =

Homework Equations

Fnet= MA

The Attempt at a Solution

Fnet= 0.0361 x 1.36
= 0.049096 Newtons
0.049096 x 1000= 49.096 MiliNewtons

Can anyone verify this for me please?

 

[TSny]

Hi, socialfox.

Your work look's good. (Picky: If the problem is stated with 3 significant figures for each quantity, then generally you would round your answer to three significant figures: 49.1 mN.

Also, "milli" has two l's.

 

[socialfox]

Thank you for replying, I had another question with that information I was supposed to calculate the force of resistance with this equation:

9.8(Mass)(Sin*angle*) - (m)(a)
so I had filled it in with these numbers below (the angle is 10.4 degrees)

9.8(36.1)(sin10.4) - 49.096 = 14.768 MilliNewtons
I understand this answer seems normal but for another question with simmilar numbers except for the degrees which is now 11.24 degrees I get this

9.8(36.1)(sin11.24) - 68.951 = 0.000749325 MilliNewtons

My problem/doubt is why is my second answer so different, also is the force of resistance correct for these questions?

Thanks for taking the time to look over this, I appreciate it :)

 

[TSny]

Your calculations look correct. However, I think it would be more consistent if you plug in SI units (.0361 kg) for the mass and then convert Newtons to milliNewtons. But' you'll get the same result.

The results seem so different because in the last case you happen to be subtracting two terms that have almost the same value.

It's hard for me to say if your "force of resistance is correct" since I don't know the set-up of the problem. Maybe you could explain how you arrived at the expression mgsinθ - ma.

 

[Nickie]

Yes, your calculation is correct. The net force in millinewtons is 49.096 mN. Keep in mind that the unit for acceleration should be m/s^2, not m/s(squared).