All High School Physics Resources
Example Questions
Example Question #91 : Forces
Miguel pushes a box with of force to the left. His sister Alexis pushes with of force to the right. What is the net force on the box?
We need to look at the net force, which is the sum of the other forces:
Since Alexis and Miguel are pushing with the same value but in opposite directions, make one of these forces negative:
Therefore, the net force upon the object is .
Example Question #92 : Forces
A dog bites down on a chew toy with of force. What is the force of the chew toy on the dog?
We need more information to solve
Use Newton's third law to solve this question. The force of the dog on the chew toy is equal in magnitude, but opposite of direction, to the force of the chew toy acting on the dog.
That means that .
Using our given values for find the force of the chew toy.
Example Question #11 : Calculating Force
If the mass of the object is and , what is the normal force on the object?
The normal force is always perpendicular to the surface upon which the object is moving, and is pointed away from said surface. That means we are looking for the value for Z in the diagram.
Observe that Z and Y are equal, but opposite forces.
If we can solve for Y, then we can find Z.
We can use our understanding of trigonometry to find an equation for Y.
If we plug in for the angle, we see:
Since we are solving for Y, we can multiply both sides by W.
Now that we know an equation for Y, we can return to our original equation to solve for Z.
From here, we can use Newton's second law to find the value of W, the total force of gravity.
Substitute this into our equation for Z.
Now we can solve for Z using the values given in the question for the angle, mass, and gravity.
Example Question #12 : Calculating Force
If the mass of the object is and , what is the normal force on the object?
The normal force is always perpendicular to the surface upon which the object is moving, and is pointed away from said surface. That means we are looking for the value for Z in the diagram.
Observe that Z and Y are equal, but opposite forces.
If we can solve for Y, then we can find Z.
We can use our understanding of trigonometry to find an equation for Y.
If we plug in for the angle, we see:
Since we are solving for Y, we can multiply both sides by W.
Now that we know an equation for Y, we can return to our original equation to solve for Z.
From here, we can use Newton's second law to find the value of W, the total force of gravity.
Substitute this into our equation for Z.
Now we can solve for Z using the values given in the question for the angle, mass, and gravity.
Example Question #13 : Calculating Force
The force acting upon a crate is . If the mass of the crate is , what is the acceleration?
For this problem use Newton's second law:
We are given the total force and the mass, allowing us to solve for the acceleration.
Example Question #16 : Calculating Force
Two dogs pull on a bone. One pulls with of force to the right and one pulls with of force to the left. What is the net force on the bone?
We must know the mass of the bone to solve
Force is a vector quantity, meaning that both magnitude and direction are important factors. Net force is calculated by summing all of the forces acting on an object.
For this question, we will assign "to the right" as the positive direction and "to the left" as the negative direction. Under these conditions, we can add the given forces to find the net force.
This means that it has a net force of to the left.
Example Question #1 : Interpreting Force Diagrams
Which of the following represents the force due to friction?
Y
Z
V
X
P
V
The force due to friction will always be parallel to the surface upon which the object is traveling. It will come directly from the center of the object, and be pointed in the opposite direction to the motion of the object.
In this diagram, V is pointed parallel to the surface and opposite to the direction of motion.
Example Question #2 : Interpreting Force Diagrams
Which of the following represents the force due to gravity?
Z
Y
X
V
W
W
Remember, in a force diagram, forces come from the center of the object. The force of gravity will always be straight down from the center of the object.
In this diagram, W is pointed directly downward.
Example Question #3 : Interpreting Force Diagrams
What is the value of angle within the triangle made by X, W, and Y?
More information is needed
When working in an inclined plane, when we break our force due to gravity into components, the angle at the top that triangle will be equal to the angle of the inclined plane.
In the diagram, the total force due to gravity is given by W. X represents the horizontal component, and is parallel to the surface of the plane. Y represents the vertical component, and is perpendicular to the surface of the plane. X and Y thus create a right angle, with W as the hypotenuse. By turning this triangle such that the right angle aligns with the right angle of the inclined plane (between Q and P), we can see that W aligns with the incline surface and Y aligns with the base, P. Based on these alignments, the angle between W and Y must be equal to the angle between the surface and P; thus, .
Example Question #4 : Interpreting Force Diagrams
Which of the following represents the normal force?
Q
X
V
-W
Z
Z
The normal force is always perpendicular to the surface on which the object is placed, and is pointed away from said surface.
In this diagram, Z is the only force that is perpendicular to the surface and in the upward direction. This force must counteract the vertical force of gravity, which will be perpendicular to the surface in the downward direction (Y).