Question

What is the net force and acceleration of a ball of mass 0.750 kilograms that is subjected to forces of 11.00 newtons and 7.00 newtons from opposite directions?

Answer 1

A force of 11N is pulling in one direction and a force of 7N is pulling in the opposite direction. First, can you tell me what the net force is?

Answer 2

well they gave me a option of 4.00 newtons net force with 5.33m/seconds^2
then 4.00 newtons with 9.33m/seconds^2
and last 11.00 newtons net force with 14.0 m/seconds^2

Answer 3

Ignore the options...that's nice to have but you should be able to calculate it :)

How would you calculate the net force?

Answer 4

idk :( i dont have notes for this...

Answer 5

The forces are in opposite directions so the signs of the forces must be opposite each other. Since the question only cares about the magnitude (and not the direction) it doesn't matter which one you make negative. The magnitude of the net force will always be the sum of the forces.

If you sum them up you get:
\[F_{net}=|F_1+F_2+F...|=|-11N+7N|=4N\]
Are you with me so far?

Answer 6

yeah until all the f's but i am willing to understand. If you could explain all those f's and what to do with them.

Answer 7

I'll try to explain it differently. My equation above is really just showing you that the magnitude of the net force will be the sum of all the forces involved.

First, I chose a coordinate system so that the left direction is negative and the right direction is positive. It ultimately doesn't matter which way you choose to be negative or positive...as long as you stick with the signs of those directions throughout the problem.

So if left is negative, we have a force of -11N pulling against a force of +7N. If you sum these together you get a net force of -4N. We don't care about the sign since we're only concerned with magnitude...which is why I put the absolute value signs around the formulas.

Make more sense now?

Answer 8

ohhhhhhhhhhhhhhhhhhh!!!!

Answer 9

so what do i do about the seconds part

Answer 10

Good :)

Now the last part is that you need to calculate the acceleration. \[F=ma\]So:\[4N=(0.750kg)a\]Solving for a you get?

Answer 11

so multiply?

Answer 12

No :)

If F=ma then you can simply rearrange the equation to get F/m = a.

Putting in the values you know you end up with:
\[\frac{4N}{0.750kg}=?\]

Answer 13

5.33

Answer 14

Yes, so 5.333 m/s^2 is the acceleration of the ball

Answer 15

awwwwww your so smart lolz thank you

Answer 16

The answer is in m/s^2 because if you remember, 1Newton = 1 kg*m/s^2. The units in the problem will cancel out and leave you with m/s^2.

Answer 17

np :)

Answer 18

If you don't understand how the units work out just let me know and I'll write it out so you can see it

Answer 19

i will definitely get to you because physics is tuff

Answer 20

It's not that tough...it just takes some getting used to :)