A chair of mass 12kg is pushed along a level floor by a force that is at an angle of θ=35.0degrees below the horizontal. The coefficient of friction between the chair and the floor is ?=0.430. The power that the force provides to move the chair in a straight line at a constant speed of 3.8m/s is?
0.43*12*9.81*3.8 = 192.35 watts
Let the applied force be P at 35 degree below the horizontal. Then its component Psin35 acts vertically downward. And component Pcos35 acts horizontally to move the chair P cos35 balances Friction force to move the chair with constant velocity Normal reaction on chair N =weight W of chair + Psin35 Friction force = co eff. of friction*normal reaction N Friction force=0.430*(12*9.8 + Psin35 ) Pcos 35 =Friction force=0.430*(12*9.8 + Psin35 ) Pcos 35 -0.430*Psin35 =0.430 *12*9.8 P[0.819 -0.43*0.573[ = 50.568 P *0.572 =59.568 P = 50.568 / 0.572 = 88.4 newton Power = force(P). velocity v=Pv cos 35=335.9*cos35 Power = 275 watt
