What is the force being applied to the box?

[ms. confused]

Hi! Is anyone willing to help me with this friction problem?

A box having a mass of 1.5kg is accelerated across a table at 1.5m/s². The coefficient of friction on the box is 0.3. What is the force being applied to the box?

 

[Pyrrhus]

Use Newton's 2nd Law

$$\sum_{i=1}^{n} \vec{F}_{i} = m \vec{a}$$

and remember

$$F_{f} = \mu N$$

 

[ms. confused]

What do I do with the friction formula?

 

[Pyrrhus]

Do you know what's the Normal force?

 

[ms. confused]

Apparently Normal force is equal to Gravitational force so 1.5kg x 9.8m/s² is 14.7N. That should be the Normal force right?

 

[Pyrrhus]

Yes, so

Do because there's only acceleration on the x-axis do the forces analysis there.

$$F_{applied} - F_{f} = ma$$

 

[ms. confused]

Do I move everything to one side of the equation to make it equal to zero?

 

[Pyrrhus]

Do I move everything to one side of the equation to make it equal to zero?

Why would you do that?

Isn't your unknown F applied?

$$F_{applied} = ma + F_{f}$$

Mass is known, acceleration is known, $\mu$ is known, and the Normal force is known (so Friction force is known).

 

[ms. confused]

Ooooooh! Gotcha! Right! Thanks a million!