An 62.0 N box of clothes is pulled 5.6 m up a 30.0掳 ramp by a force of 95 N that points along the ramp. If the coefficient of kinetic friction between the box and the ramp is 0.22, calculate the change in the box's kinetic energy.
Can u show me what to do???
How long will it take a 1620 W motor to lift a 285 kg piano to a sixth-story window 16.0 m above? again please
Physics???
1.
Force equation
Total force Ft equal to the difference between the force of pull Fp downward force Fd and force of friction f.
Ft=Fp- Fd - f
Ft=Fp - Wsin(30) - uWcos(30)
Ft=95 - 62.0 sin(3) - 0.22 x 62.0 cos(30)
Ft=95.0 - 31 -11.8 =52.2 N
Ke=0.5mV^2
Change in kinetic energy DKe
DKe=K2-K1 since the box initial velocity was 0 k1=0
DKe=K2=0.5mV^2 also
since V=at and t=sqrt(2S/a)
V= sqrt(2Sa) where a= Ft/m=gFt/W [since W=mg]we have
DKe=0.5 W/g (2 S gFt/W)
DKe= ( S Ft)= 5.6 x 52.2=292 J (notice that DKe = Work done by Ft)
2. P=E/t
Pe= E= mgh
t= E/P= mgh/P
t=285 x 9.81 x 16.0 / 1620
t=27.6 sec
