Answer:
44.6 m
Explanation:
From the law of conservation of energy, the total energy at the top of the ramp, E equals the total energy at the bottom of the ramp.
E = E'
U₁ + K₁ + W₁ = U₂ + K₂ + W₂ where U₁ = potential energy at top of ramp = mgh where = height of ramp, K₁ = kinetic energy at top of ramp = 1/2mv₁² where v₁ = speed at top of ramp = 1.8 m/s, W₁ = work done by friction and air resistance at top of ramp = 0 J, U₂ = potential energy at bottom of ramp = 0 J(since the skier is at ground level h = 0), K₂ = kinetic energy at bottom of ramp = 1/2mv₂² where v₂ = speed at bottom of ramp = 28.0 m/s, W₁ = work done by friction and air resistance at bottom of ramp = 3500 J
Substituting the values of the variables into the equation, we have
U₁ + K₁ + W₁ = U₂ + K₂ + W₂
mgh + 1/2mv₁² + W₁ = U₂ + 1/2mv₂² + W₂
mgh + 1/2m(1.8 m/s)² + 0 J = 0 J + 1/2m(28 m/s)² + 3500 J
9.8 m/s² × 75 kg h + 1/2 × 75 kg (3.24 m²/s²) + 0 J = 0 J + 1/2 × 75 kg (784 m²/s²) + 3500 J
(735 kgm/s²)h + 75 kg(1.62 m²/s²) = 75 kg(392m²/s²) + 3500 J
(735 kgm/s²)h + 121.5 kgm²/s² = 29400 kgm²/s² + 3500 J
(735 kgm/s²)h + 121.5 J = 29400 J + 3500 J
(735 kgm/s²)h + 121.5 J = 32900 J
(735 kgm/s²)h = 32900 J - 121.5 J
(735 kgm/s²)h = 32778.5 J
h = 32778.5 J/735 kgm/s²
h = 44.6 m
So, the maximum height of the ramp for which the maximum safe speed will not be exceeded is 44.6 m.
