Question

A piston motion moves a 50 lbm hammerhead vertically down 3 ft from rest to a velocity of 150 ft/s in a stamping machine. What is the change in total energy of the hammerhead?  

Answer 1

C.V. Hammerhead

The hammerhead does not change internal energy i.e. same P,T

E₂ – E₁ = m(u₂ – u₁) + m(1/2V₂² - 0) + mg (h₂ - 0)

= 0 + [ 50 × (1/2) ×1502 + 50 × 32.174 × (-3)] / 32.174

= [562500 – 4826]/32.174

= 17 333 lbf-ft

= (17333/778 ) Btu

= 22.28 Btu