Question

A civil engineer must design a wheelchair-accessible ramp next to a set of steps leading up to a building. The height from the ground to the top of the stairs is 2 ft. Based on ADA codes, the slope must be 1:12 or less. Slope is equal to the rise of the ramp divided by the run of the ramp.
A) Using the ADA code, what is the allowable minimum length of the ramp base?

B) Using the known height and calculated base length, what is the length of the slope of the ramp?

C) What is the ideal mechanical advantage of the ramp?D) If a person and wheelchair have a combined weight of 165 lb, how much ideal effort force is required to travel up the ramp?

Answer 1

Answer:

A) B = 24 ft

B) H = 24.08 ft

C) M.A = 12.04

D) P = 13.7 lb

Explanation:

A)

Minimum allowable length of base of ramp can be found as follows:

Slope = H/B

where,

Slope = 1/12

H = Height of Ramp = 2 ft

B = Length of Base of Ramp = ?

Therefore,

1/12 = 2 ft/B

B = 2 ft * 12

B = 24 ft

B)

The length of the slope of ramp can be found by using pythagora's theorem:

L = √H² + B²

where,

H = Perpendicular = height = 2 ft

B = Base = Length of Base of Ramp = 24 ft

L = Hypotenuse = Length of Slope of Ramp = ?

Therefore,

H = √[(2 ft)² + (24 ft)²]

H = 24.08 ft

D)

The mechanical advantage of an inclined plane is given by the following formula:

M.A = L/H

M.A = 24.08 ft/2 ft

M.A = 12.04

D)

Another general formula for Mechanical Advantage is:

M.A = W/P

where,

W = Ideal Load = 165 lb

P = Ideal Effort Force = ?

Therefore,

12.04 = 165 lb/P

P = 165 lb/12.04

P = 13.7 lb