Question

A wooden block with mass 1.80 kg is placed against a compressed spring at the bottom of a slope inclined at an angle of 34.0 ? (point A). When the spring is released, it projects the block up the incline. At point B, a distance of 6.00 m up the incline from A, the block is moving up the incline at a speed of 6.45 m/s and is no longer in contact with the spring. The coefficient of kinetic friction between the block and incline is ?k = 0.55. The mass of the spring is negligible. Calculate the amount of potential energy that was initially stored in the spring.

Answer 1

Workdone by friction = final mechanical energy - initial mechanical energy

initial mchanical energy = final mechanical energy - workdone by friction

the amount of potential energy that was initially stored in the spring = final mechanical energy - workdone by friction

=(1/2)*m*v^2 + m*g*h - fk*d*cos(180)

= (1/2)*m*v^2 + m*g*h - mue_k*m*gcos(34)*d*cos(180)

= (1/2)*1.8*6.45^2 + 1.8*9.8*6*sin(34) - 0.55*1.8*9.8*cos(34)*6*(-1)

= 145 J <<<<<<<--------------Answer