Answer:
Force (P) : Positive
Normal Force (Fn) : Zero
Weight (mg) : Zero
Kinetic Frictional Force (fk) : Negative
Explanation:
The work done by a force on an object is given by the following formula:
W = F.d
W = F d Cosθ
where,
W = Work Done
f = Force Applied
d = displacement
θ = Angle between force and displacement
FOR FORCE (P):
Since, force P is parallel to the motion of the box. Therefore, θ = 0°
Hence,
W = P d Cos 0°
W = P d(1)
W = Pd
Therefore, work done by force (P) is Positive.
FOR NORMAL FORCE (Fn) AND WEIGHT (W):
Since, normal force and weight are perpendicular to the motion of the box. Therefore, θ = 90°
Hence,
W = Fn d Cos 90°= mg d Cos 90°
W = Fn d(0) = mg d (0)
W = 0
Therefore, work done by Normal Force (Fn) and Weight (mg) is Zero.
FOR KINETIC FRICTIONAL FORCE (fk):
Since, kinetic frictional force acts in the opposite direction of motion of the box. Therefore, θ = 180°
Hence,
W = fk d Cos 180°
W = fk d(-1)
W = -fk d
Therefore, work done by Kinetic Frictional Force (fk) is Negative.
