Sure, knockback 'can' be done quite simply in the traditional platformer/rpg sense. However objects such as cars can be more difficult due to wheel motion and the shape.
On a side note. I recommend reading up on vector maths/motion physics, as it will help with all games you may work on.
Read part 1-3:
http://blog.wolfire.com/2009/07/linear-algebra-for-game-developers-part-1/What kind of objects are needing to collide? Are you requiring knockback like in the platformer Mario, pong bat & ball, cars, perhaps something else?
The simplest form is probably by moving one object in the opposite direction of the other object. You're going to need a motion system for smooth knockback (acceleration, friction, optional gravity):
//Non-code example
directionRadians = atan2(y1 - y2, x1 - x2) // Angle between objects, negate the value for reverse direction
directionDegrees = (directionRadians * 180) / PI // If your game uses degrees instead of radians, convert
object1.setDirection(-directionDegrees) // Imaginary motion function for setting the current direction of the force
object1.setAcceleration(30) // Imaginary motion function to set the force's magnitude
object2.setDirection(directionDegrees)
object2.setAcceleration(30)
If you want to reverse from the collision point, simply work out the positions of each object relative to the collision point, and then use those coordinates as the position.
