A 80 N force is needed to slide a 550 kg box across a Hat su

A 80 N force is needed to slide a 55.0 kg box across a Hat surface at a constant velocity. What is the coefficient of kinetic friction betw een the box and the floor? (Use g = 9.8 m/s^2.) A) 0.13 B) 0.15 C) 0.16 D) 0.18 5) A 10.0 kg block on a table is connected by a string to a 63 kg mass, which is hanging over the edge of the table. Assuming that frictional forces may be neglected, what is the magnitude of acceleration of the 10.0 kg block when the other block is released? (See the figure.) A) 7.5 m/s^2 B) 8.1 m/s^2 C) 9.0 m/s^2 D) 8.5 m/s^2 6) A child does 350 J of work while pulling a box from the ground up to his tree house with a rope, at a constant speed. The tree house is 6.4 m above the ground. What is the mass of the box? A) 4.3 kg B) 2.6 kg C) 5.2 kg D) 5.6 kg 7) An object moves in a circular path at a constant speed. Compare the direction of the object\'s velocity and acceleration vectors. A) Both vectors point in the same direction.? B) The vectors are perpendicular. C) The vectors point in opposite directions. D) The question is meaningless, since the velocity is zero. E) The question is meaningless, since the acceleration is zero.

Solution

4) Velocity is costant a = 0 , g = 9.81 m/s

F = mu m g

80 = mu * 55 * 9.8

mu = 0.15

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5) sum of forces = (m1 + m2) * a

(9.81 * 63 ) = 73 * a

a = 8.5 m/s²