kulwant work-energy principle conservation of mechanical energy work done = change in k.e. + change...
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kulwant
Work-Energy PrincipleConservation of Mechanical Energy
Work done = Change in K.E. + Change in PE
A rough slope is inclined at tan-1( ¾ ) to the horizontal. A box of mass 25 kg slides from rest a distance of 20 m down a line of greatest slope, at which point it has developed a speed of 14 m/s. Find the work done against friction and the coefficient of friction.
Gain in K.E. = 0.5 25 142 = 2450Loss in P.E. = 25 9.8 20 3/5 = 2940
Loss in energy = 490 = WD against friction
kulwant
Work-Energy Principle
Loss in energy = 490J = WD against friction
WD = Fd Friction = 490 20 = 24.5 N
F
R cosR mg
= 24. 5 259.8(4/5) = 0.125
kulwant
Work-Energy Principle
A bullet of mass 20 grams is fired horizontal into a vertical target of 15 cm thickness with a speed 250 m/s. If the target offers a resistance of 3600N, with what speed will the bullet emerge on the far side?
K.E. = 0.5 0.020 2502 = 625 J
WD against resistance = 3600 0.15 = 540 J
Energy level on far side = 8521
2KE mv
v = 92.2 m/s