a
Make an object move opposite the applied force.
b
Can change an object's speed but not direction.
c
Maintain the constant motion of an object.
d
Cause the motion of an object to change.
a. Friction - friction acts opposite to the direction of the applied force, thus causing the object to move in the opposite direction.
b. Acceleration - by changing an object's acceleration, its speed can be changed while the direction remains the same.
c. Balanced forces - when the forces acting on an object are balanced, the object will continue to move at a constant speed and in the same direction.
d. Unbalanced forces - when unbalanced forces are applied to an object, they cause the object to accelerate in the direction of the net force, thus changing its motion.