An old refrigerator has fallen into a ditch, and your friend wants to pull it ou
ID: 1998873 • Letter: A
Question
An old refrigerator has fallen into a ditch, and your friend wants to pull it out using a rope stretched over a smooth rock as a pulley. You estimate the mass of the refrigerator as 100 kg and the mass of your friend's car as 1000 kg. The ditch is at a slope of 35 degree with respect to the horizontal, and the car is on a 15 degree slope. Friction between the fridge and the slope is high, with a coefficient of 0.9 for static friction and 0.41 for kinetic friction. As a first approximation you neglect friction between the car and the slope. Can the car pull the fridge out of the ditch just by its larger weight, without having to apply extra force from the engine? Your answer must be organized, clear, and complete. See the attached mastery problem rubric for a reminder of what should be included for a perfect score.Explanation / Answer
let M = 1000 kg
m = 100 kg
component of gravity acting on the car alongt the ramp,
Fg_car = M*g*sin(15)
= 1000*9.8*sin(15)
= 2536 N
If car Engine does not apply any force, the maximum tension in the rope,
Tmax = Fg_car
= 2536 N
Normal force acting on the refregerator,
N = m*g*cos(35)
Force acting on the fridge along the ramp,
F_fridge = m*g*sin(35) + mue_s*N
= m*g*sin(35) + mue_s*m*g*cos(35)
= 100*9.8*sin(35) + 0.9*100*9.8*cos(35)
= 1284 N
ceraly, Tmax > F_fridge
so, The can can pull the fridge. <<<<<<<---------Answer