A 17.1 kg block is dragged over a rough, hor-
izontal surface by a constant force of 93.1 N
acting at an angle of angle 28.5 above the
horizontal. The block is displaced 77.2 m and
the coefficient of kinetic friction is 0.203.
A. Find the work done by the 93.1 N force.
The acceleration of gravity is 9.8 m/s2 .
Answer in units of J
B. Find the magnitude of the work done by the
force of friction.
Answer in units of J
C. What is the sign of the work done by the
frictional force?
D. Find the work done by the normal force.
Answer in units of J
E. What is the net work done on the block?
Answer in units of J
izontal surface by a constant force of 93.1 N
acting at an angle of angle 28.5 above the
horizontal. The block is displaced 77.2 m and
the coefficient of kinetic friction is 0.203.
A. Find the work done by the 93.1 N force.
The acceleration of gravity is 9.8 m/s2 .
Answer in units of J
B. Find the magnitude of the work done by the
force of friction.
Answer in units of J
C. What is the sign of the work done by the
frictional force?
D. Find the work done by the normal force.
Answer in units of J
E. What is the net work done on the block?
Answer in units of J
-
Work is F·d
The vector dot product works like this: multiply the magnitude of one vector by the component of the other vector that is in the same direction as the first vector.
A. The displacement is horizontal. Calculate the horizontal component of the force, multiply that by the displacement.
B. Calculate the vertical component of the dragging force, and the gravitational force, then use those to calculate the normal force and then the magnitude of the friction. Friction is always in the direction opposite motion, so its horizontal component will be easy to find.
C. If the direction of the displacement is positive, then is the frictional force positive or negative?
(Equivalently, if the direction of the friction is positive, then is the displacement positive or negative?)
D. Calculate the horizontal component of the normal force, multiply that by the displacement.
E. Sum the work done by all forces (the dragging, friction, normal, and gravitational forces).
The vector dot product works like this: multiply the magnitude of one vector by the component of the other vector that is in the same direction as the first vector.
A. The displacement is horizontal. Calculate the horizontal component of the force, multiply that by the displacement.
B. Calculate the vertical component of the dragging force, and the gravitational force, then use those to calculate the normal force and then the magnitude of the friction. Friction is always in the direction opposite motion, so its horizontal component will be easy to find.
C. If the direction of the displacement is positive, then is the frictional force positive or negative?
(Equivalently, if the direction of the friction is positive, then is the displacement positive or negative?)
D. Calculate the horizontal component of the normal force, multiply that by the displacement.
E. Sum the work done by all forces (the dragging, friction, normal, and gravitational forces).