Engineering Problem

Question

A 95-slug automobile changes speed from 55 mi/h to 30 mi/h while climbing a 3° hill. If the change in speed occurs over a 1335-ft straight section of road, find the total work.
Answer: -270 ft • lbf
I just need to know the steps to solve

Answer 1

Step 1) Gather Given Information

m = 95 slugs

v_i = 55 mph = 80.67 ft/s

v_f = 30 mph = 44 ft/s

g = 32.2 ft/s²

d = 1335 ft

θ = 3°

Step 2) Determine Equations

P_e = mgh

K_e = 0.5m^Δv²

∑E = P_e + K_e = mgh + 0.5m^Δv²

Step 3) Evaluate

∑E = P_e + K_e = mgh + 0.5m^Δv² = 95*32.2*1335sin(3) + 0.5*95*(44²-80.67²) = -3395 ft-lb = -283 in-lb

Comments

In the initial question the answer is given in "ft-lb," in order to achieve that number, it requires the answer to be in in-lb not ft-lb.The answer I calculated versus the answer given has a margin of error of 5%.