Density <em>ρ</em> is mass <em>m</em> per unit volume <em>v</em>, or
<em>ρ</em> = <em>m</em> / <em>v</em>
Solving for <em>v</em> gives
<em>v</em> = <em>m</em> / <em>ρ</em>
So the given object has a volume of
<em>v</em> = (130 g) / (65 g/cm³) = 2 cm³
The formula for both is v(t) = v0 + a*t
b) v(8) = 0 + 6m/s^2 *8s = 48 m/s
now we know the beginning (2) and end speed (14), but not the time:
c) 14 = 2 + 1.5*t => t = (14-2)/1.5 = 8 seconds
Acceleration = v-u/t
= (45-30)/15
= 1 km/h
Distance = ut + 1/2 at^2
s = [30 x 15] + 1/2 x 1 x 15^2
= 562.5 km
Hope this helps