You are pushing a 150-kg wooden crate in a straight line a distance of 4.5 m across a wooden floor. the crate is speeding up at 0.48 m/s2. the static and kinetic coefficients of friction are 0.42 and 0.30, respectively. what is the work done by you on the crate?

 Since the crate is moving use the kinetic coefficient of friction. Ff = 150 * 9.8 * 0.30 = 441 N Work done by friction force = 441 * 4.5 = 1984.5 N * m 
Since the crate is accelerating, the force with which you push the crate must be greater than the friction force. Net force = F – 441 = 150 * 0.33 F = 441 + 49.5 = 490.5 N This is the force which you exerted

The earths atmosphere is made up of nitrogen and oxygensolids turning into gases is called sublimation.