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The block moves up an incline with constant speed. What is the total work Wtotal done on the block by all forces as the block moves a distance L = 4.00 m up the incline? Include only the work done after the block has started moving at constant speed, not the work needed to start the block moving from rest.

Respuesta :

lykosz88

Answer:

zero

Explanation:

Since the work on the block is the sum of the works done by every force acting on the block:

Wtotal = Wk + Wn + Wg

Wk ; work done by the friction force, Fk

Wn: work done by the normal force, Fn

Wg: work done by the gravity force, Fg

Since, by definition of work:

Wk = Fk*L*cos(180°) = - Fk*L

Wn = Fn*L*cos(90°) ) = 0

Wg = Fg*L*cos(90-∅) = Fg*L*sin(∅)

Wtotal = - Fk*L + 0 + Fg*L*sin(∅) ----- (1)

Since the block moves to constant velocity, by 2° Newton's law: the sum of all forces are zero.

Using diagram of all forces, is posible demostrate:

Fk = Fg*sin(∅)

Reeplacing in the (1) expression:

Wtotal = 0

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