How is direction of frictional force of an object on bed of moving object same as direction of moving object? Imagine there is an object placed on bed of a moving truck, I understood from a previous answer that the direction of frictional force acting on object will be same as direction of moving truck.
I haven't quite understood this because I study in High school and I don't know about Inertial frames or something, so can you explain it in simpler fashion? Why is direction of friction same as moving truck because I know that frictional force always acts in opposite directions
 A: Il try to keep things simple as you wanted.

I think your confusion is that since friction is an opposing force should it not oppose the direction of motion? That is absolutely correct in non-accelerating frames
But the given situation is an accelerating one.
An important term:
pseudo force (fictitious force to make newtons laws applicable in non-inertial frames )
when you sit in an accelerating car do you feel something pushing you back? (it's actually the car pushing into you)
That my friend is pseudo force in your frame of reference.
Now for your given situation, there will be pseudo force trying to push it back and friction opposing it forward. Therefore friction acts along the direction of motion.
A: The frictional force acts in the opposite direction to the relative motion (or potential motion) between the object and the truck. If the truck is accelerating forward then the object’s inertia means it tries to move backwards relative to the truck, so the frictional force acts in the forward direction.
A: Simply put, as a truck accelerates the friction between the truck bed and the cargo will act to pull the cargo along with the truck. Therefore the friction force is acting to move the cargo in the same direction as the truck. Note: I have substituted the words cargo for object and truck for moving object to avoid confusion.
