Answer:
ρ = M / V = 2 g / .5 cm^3 = 4 g/cm^3
Your diagram should include four forces:
• the box's weight, pointing down (magnitude <em>w</em> = 43.2 N)
• the normal force, pointing up (mag. <em>n</em>)
• the applied force, pointing the direction in which the box is sliding (mag. <em>p</em> = 6.30 N, with <em>p</em> for "pull")
• the frictional force, pointing oppoiste the applied force (mag. <em>f</em> )
The box is moving at a constant speed, so it is inequilibrium and the net forces in both the vertical and horizontal directions sum to 0. By Newton's second law, we have
<em>n</em> + (-<em>w</em>) = 0
and
<em>p</em> + (-<em>f</em> ) = 0
So then the forces have magnitudes
<em>w</em> = 43.2 N
<em>n</em> = <em>w</em> = 43.2 N
<em>p</em> = 6.30 N
<em>f</em> = <em>p</em> = 6.30 N
