Question

A bulldozer pushes 1000 lbm of dirt 300 ft with a force of 400 lbf. It then lifts the dirt 10 ft up to put it in a dump truck. How much work did it do in each situation?

Answer 1

W = ∫ F dx = F ∆x

= 400 lbf × 300 ft

= 120 000 lbf-ft

= 154 Btu

W = ∫ F dz = ∫ mg dz = mg ∆Z

= 1000 lbm × 32.174 ft/s² × 10 ft / (32.174 lbm-ft / s²-lbf)

= 10 000 lbf-ft = 12.85 Btu