Answer:
v = 11 m/s is her final speed
Explanation:
work done by gravity = m g Δh = 40×9.8×10 = 3920 Joules
Work done by friction = - force×distance = - 20×100 = - 2000 Joules
[minus sign because friction force is opposite to the direction of motion]
Initial K.E. = (1/2) m u^2 = (1/2) × 40 × 5^2 = 500 Joules
Now, by work energy theorem
Work done = change in kinetic energy.
Final K.E. = initial K.E. + total work = 500 + 3920 - 2000 = 2420 Joules
Now, Final K.E. = (1/2) m v^2 [final speed being v= speed at the bottom]
⇒ 2420 = (1/2)×40×v^2
⇒ 121 = v^ 2
v = 11 m/s is her final speed
Answer:
<em>The volume of the feathers in ft³ = 16 ft³</em>
Explanation:
Density: This can be defined as the ratio of mass of a body to the corresponding volume of that body. The S.I unit of Density is kg/m³
Mathematically it can be expressed as,
D = m/v ................................... Equation 1
making v the subject of the equation above,
v = m/D ............................. Equation 2
Where D = Density of the feathers, m = mass of the feathers, v = volume of the feathers.
Given: D = 0.50 lbs/ft³, m = 8.0 lbs.
Substituting into equation 2
v = 8/0.5
v = 16 ft³
<em>Thus the volume of the feathers in ft³ = 16 ft³</em>
