The coefficient of kinetic friction between a 20kg box and the floor is 0.4. How
ID: 1430040 • Letter: T
Question
The coefficient of kinetic friction between a 20kg box and the floor is 0.4. How much work does a pulling force do on the box in pulling it 8m across the floor at constant speed if the pulling force is directed 37 degree above the horizontal? A 30 kg sled is sliding on a frictionless sheet of ice at a velocity of 4 m/s. The sled encounters a rough patch of ice and begins to slow down. After traveling on the rough patch of ice for 3 m, the sled's velocity is 2 m/s. Determine the coefficient of friction between the rough ice and the sled. A 1 kg particle moving along the x-axis experiences the force shown in the graph. If the particle's speed is 2m/s at x=0m, what is its speed when it gets to x=5m?Explanation / Answer
5) let F is the applied force.
As the block is moving with constant velocity the net force on it must be zero.
Fnety = 0
N + F*sin(37) - m*g = 0
N = m*g - F*sin(37)
now Apply, Fnetx = 0
F*cos(theta) - N*mue_k = 0
F*cos(theta) - (m*g - F*sin(37))*mue_k = 0
F*cos(theta) - m*g*mue_k + F*sin(37)*mue_k = 0
F*(cos(theta) + mue_k*sin(37)) = m*g*mue_k
F = m*g*mue_k/(cos(37) + mue_k*sin(37))
= 20*9.8*0.4/(cos(37) + 0.4*sin(37))
= 75.4 N
so, workdone by applied force, W = F*cos(37)
= 75.4*8*cos(37)
= 481.74 J <<<<<<<<----------------Answer