Question

Calculate the accelerating force needed to change the speed of 20lb object from 18ft/s to 50ft/s in a distance of 40ft

Answer 1

$v^{2}=u^{2}+2as$

$50^{2} = 18^{2}+2as$

$80a=2500-324$

$80a=2176$

$a=27.2fts^{-2}=8.29056ms^{-2}$

$m=20\times 0.453592=9.072kg$

$F=ma=9.072\times8.29056=75.21N$