What is the minimum work needed to push a 1200 kg car 370 m up along a 17.5° incline?
(a) Ignore friction.
J
(b) Assume the effective coefficient of friction retarding the car is 0.25?
J
2007-03-12 07:30:29 · 2 answers · asked by nafiseh g 1 in Science & Mathematics ➔ Physics
Break this problem into a horizonal and vertical distance component.
Knowing the incline (17.5 deg) and the hypotenuse of the triangle (370 m) you can calculate the horizontal length and vertical length component of the incline.
a) ignore friction... pushing the car in the horizontal needs no work since it takes no forces to push it horizontal (frictionless).
However, what work that need to be done is lifting the car vertically. W = mass x gravity x height.
b) now you have work done in the horizontal because of friction.
work in the horizontal = friction force x horizontal distance
Total work = answer a + work in the horizontal
I hope that helps.
2007-03-12 07:41:06 · answer #1 · answered by Dave C 7 · 0⤊ 0⤋
Ignoring friction, just use the potential energy, mgh
You are given m and we know g.
h (vertical height) is just the distance of the ramp times the sine of the angle.
Adding friction is going to add to that.
How much will it add?
The work is the friction force times the distance.
The normal force on the car (its weight, mg, times the cosine of the angle). Multiply that normal force times the friction coefficient to get the friction force. Then multiply by the distance to get the extra work.
2007-03-12 07:37:08 · answer #2 · answered by Anonymous · 0⤊ 0⤋