A man is pushing block, m= 45 [kg], with force F=480 [N]. Determine the power, P
ID: 1387594 • Letter: A
Question
A man is pushing block, m= 45 [kg], with force F=480 [N]. Determine the power, P [W], supplied by the man when t=4 [s]. The coefficient of kinematic friction is mk=0.3. Initially the crate is at rest. Angle ?=30o.
20 (286.16 - 326.16)
A man is pushing block, m= 45 [kg], with force F=480 [N]. Determine the power, P [W], supplied by the man when t=4 [s]. The coefficient of kinematic friction is mk=0.3. Initially the crate is at rest. Angle ?=30o.
Selected Answer:12947.90
Correct Answer:306.16
Answer range +/-20 (286.16 - 326.16)
Explanation / Answer
Power P = Work done /time
Work done W = Fnet*S
Fnet = F-(m*g*sin(30))-(mk*m*g*cos(30))
Fnet = 480-(45*9.81*0.5)-(0.3*45*9.81*cos(30)) = 144.6 N
Fnet = m*a
accelaration a = Fnet/m= 144.6/45 = 3.21 m/s^2
distance travelled is S = 0.5*a*t^2 = 0.5*3.21*4^2 = 25.68 m
Work dome W = 144.6*25.68
power P = W/t = 144.6*25.68/4 = 928.332 W
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