A6 kg box has a coefficient of friction with a table of 0.7, and it’s slowing down across the table with no pushing force. what is the acceleration of the box?

a. 42 m/s^2
b. 7 m/s^2
c. 6 m/s^2
d. 0.7 m/s^2

B. 7 m/s²

Explanation:

Draw a free body diagram of the box.  There are three forces:

Normal force N pushing up.

Weight force mg pulling down.

Friction force Nμ pushing against the direction of motion.

Sum of forces in the y direction:

∑F = ma

N − mg = 0

N = mg

Sum of forces in the x direction:

∑F = ma

-Nμ = ma

-mgμ = ma

a = -gμ

a = -(9.8 m/s²) (0.7)

a ≈ -7 m/s²

The magnitude of the box's acceleration is 7 m/s².

an electric circuit

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it