Name_____________________________
Force Diagrams
Balanced Forces
When an object rests on a surface such as the ground, its weight is balanced by the reaction force
from the ground. The ground pushes up against the object. The reaction force is what you feel on your
feet as you stand still. Without this balancing force you would sink into the ground.
The weight of a book lying on a table is balanced by the reaction force from the table top.
Unbalanced Forces
When two forces are acting on an object that are not equal in size.
The size of the overall force acting on an object is called the resultant force. If the forces are balanced,
this is zero. In the truck example above, the resultant force is the difference between the forces which is
100-60 = 4 Newtons.
FORCES PRACTICE
1. Are any of the forces acting on the freezer balanced?
If so which ones?
Fpus
W 2. Are any of the forces acting on the freezer unbalanced?
If so which ones?
N Ffriction DRAW VECTOR ARROWS SHOWING THE FORCES BEING APPLIED IN EACH SITUATION BELOW:
3.) A dog laying on the floor waiting for his dinner.
5.) A librarian pushing a book cart.
4.) A monkey falling out of a tree.
6.) Student wearing a backpack and holding books
For each of diagram, determine the net force acting on the object. Follow the format for showing your
work shown in (a). Then, write whether or not there will be a change in motion. If yes, write the direction
the object will move in.
EXAMPLE:
2 N 4 N Net force: 4 N – 2 N = 2 N to the left.
Change in motion: The box will move to the left.
7.)
2 N 4 N Net force: Net force: Change in motion: Change in motion: 5 N Net force: Change in motion: 5 N 10.)
8 N 9.) 8)
5 N 2 N Net force: Change in motion: 10 N 10 N Calculate the net force on the object described in each situation. Draw a force diagram for each and
show the directions of forces as well as the total net force and direction of net force.
11.) A box is being pushed by two stellar science students, one on each side of the box. Mike is pushing
the box with a force of 10 N to the left. Mike is pushing the box with a force of 15 N to the right. Who is the
stronger individual and what is the net force and direction on the box?
12.) During tug of war Janelle felt she was supergirl and attempted to beat her older brother Raymond.
Janelle with one arm on the rope and the other at her side applied a 100 N force to the left, while Raymond
applied a 100 N force with both hands to the right. What is the net force and direction on the rope?
13.) In a third period battle the girls were able to overcome the boys 3 times in the tug of war . The boys
had 8 individuals each pulling with a force of 30 N. The 10 girls were able to pull the rope toward them with
a net force of 50 N. What is the net force and the direction of the rope?
14.) Create your own scenario demonstrating net force on an object. Then give your scenario to partner
to see if they can come up with the drawing.