Balanced and Unbalanced Forces Standard 8-5.5 Analyze the resulting effect of balanced and unbalanced forces on an object’s motion in terms of magnitude and direction.

Forces a push or a pull What is a force? magnitude (strength) & direction What is a force? Forces have what 2 factors?

Representing Forces as arrows How can forces be represented? the magnitude of the force in the direction of the force the resulting (net) force & direction How can forces be represented? What does the length of the arrow represent? Where does the head of the arrow point? What can be determined with these arrows?

Balanced Forces Characteristics of balanced forces: If balanced forces act on an object in opposite directions & equal in strength, then.. Objects that are not moving will.. cause no change in the motion of an object they do not cause a change in the speed/magnitude or direction of a moving object not start moving if acted upon by balanced forces

Examples of Balanced Forces In arm wrestling, where there is no winner, the force exerted by each person is equal, but they’re pushing in opposite directions. The resulting force (net force) is zero. (0) 5N 5N In tug of war, if there is no movement in the rope, the two teams are exerting equal, but opposite forces that are balanced. Again net force = zero (0).

Unbalanced Forces Characteristics of unbalanced forces: When two unbalanced forces are exerted in opposite directions… they are not equal they always cause the motion of an object to change the speed and/or direction the object is moving their combined force is equal to the difference between the two forces

Cont. What affects the resulting motion? Where is this combined force exerted? the magnitude and direction of the net force in the direction of the larger force

Examples of Unbalanced Forces If two students push on opposite sides of a box sitting on the floor, the student on the left pushes with less force (small arrow) on the box than the student on the right side of the box (long arrow). The resulting action (net force: smaller arrow to the right of the =) shows the box will change its motion to the direction of the greater force: 5N 10N = 5N

Examples cont. In tug of war, if one team pulls harder than the other, the resulting action (net force) will be that the rope will change its motion in the direction of the force with the greater strength/magnitude. 5N 10N = 5N

Examples Cont. If unbalanced forces are exerted in the same direction, the resulting force (net force) will be the sum of the forces in the direction the forces are applied. If two people pull on an object at the same time in the same direction, the applied force of the object will be the result of their combined forces (net force or longer arrow to the right of the = sign) (See next slide)

Examples Cont. 5N + = 10N 15N

Adding and Subtracting Unbalanced Forces What do you do when the forces act in the same direction? What do you do when the forces act in opposite directions? add the forces subtract them

Motion of Unbalanced Forces Unbalanced forces also cause nonmoving objects to... If there is no net force acting on the object.. If there is net force acting on an object change motion the motion does not change the speed of the object will change in the direction of the net force