All High School Physics Resources
Example Questions
Example Question #1 : Forces
The same force is applied to two different objects. One object has a mass of , and the other has a mass of . Which one has the greater acceleration?
We need to know the value of to solve
We need to know the value of the force applied to solve
The accelerations are equal
The equation for a force is:
We can write this equation in terms of each object:
We know that the force applied to each object will be equal, so we can set these equations equal to each other.
We know that the second object is twice the mass of the first.
We can cancel out the mass from each side, leaving a relationship between the two accelerations.
The acceleration on the first mass is twice the acceleration on the second; thus, the acceleration of the lighter mass is greater.
Example Question #5 : Understanding The Relationship Between Force And Acceleration
Lance pushes a crate of mass with newtons of force. What is the resultant acceleration?
The formula for force is Newton's second law:
We are told in the question to use for the mass and for the force.
Now we can isolate the acceleration.
This also makes sense from a units perspective. Units for force are Newtons, which can be written as:
In our equation, we can see that Newtons are divided by mass:
This would result in the units for acceleration.
Example Question #6 : Understanding The Relationship Between Force And Acceleration
A ball begins to roll with a velocity of . If no outside forces act upon it, what will be its velocity in ?
If there are no forces acting upon the object, then there is no acceleration. If there is no acceleration, then the object will move with a constant velocity.
Mathematically, we can look at Newton's second law and the formula for acceleration.
We know that the force is zero.
Since we know that the mass cannot be zero, the acceleration must be zero.
We can now use the formula for acceleration to see the effects on velocity.
We know that the acceleration is zero and that the time is ten seconds.
In order for this to be true, the initial and final velocities must be equal.
Example Question #7 : Understanding The Relationship Between Force And Acceleration
Two dogs are pulling on a bone in opposite directions. If the bone does not move, what conclusions can be drawn?
The dogs are pulling with equal force, but in opposite directions
We need to know the mass of the bone to draw any conclusions
We need to know the acceleration on the bone in order to draw any conclusions
The two forces are equal in size and going in the same direction
We need to know the weight of the dogs in order to draw any conclusions
The dogs are pulling with equal force, but in opposite directions
If the bone does not move, then we know that the resultant acceleration on it is zero. That means that the net force must also equal zero.
In other words, the sum of the two forces acting on the bone must be zero.
Since the forces are pulling in opposite directions, one force must be in the negative direction.
From here, it's simple manipulation to see that the forces are equal.
The forces are equal in size, but going in opposite directions.
Example Question #8 : Understanding The Relationship Between Force And Acceleration
An ice skater skates on a frictionless surface with a velocity of . If no forces act upon him, what is his velocity after ?
We need to know the displacement of the skater in order to solve
We need to know the skater's mass in order to solve
If no forces are acting upon the skater and he is on a frictionless surface, then that means he has no net acceleration.
Mathematically, we can see this relationship from Newton's second law:
Presumably the skier has mass, therefore the acceleration must be zero.
If an object moves with a velocity and there is no acceleration, then the velocity remains constant. His velocity after five second will be equal to his initial velocity.
Example Question #9 : Understanding The Relationship Between Force And Acceleration
How much force is required to move a filing cabinet ?
We need to know the coefficient of friction between the cabinet and the floor
We need to know the final velocity of the cabinet
We need to know the coefficient of friction between the cabinet and the floor
There is insufficient information to solve. Force is the product of mass and acceleration. While we are given the mass, we are not given an acceleration.
If we assume that we are looking for the minimum force required to move the cabinet, then the force would be equal to the force of friction.
Substitute the equations for frictional force and Newton's second law.
Normal force is equal to the force of gravity.
The masses cancel out and we know the acceleration due to gravity is constant.
This equation is unsolvable as we do not know , the coefficient of friction between the cabinet and the floor. We cannot find the acceleration of the cabinet, meaning we cannot find the force.
Example Question #10 : Understanding The Relationship Between Force And Acceleration
A car rounds a perfectly circular turn at a constant speed. This causes the acceleration to __________.
decrease
remain constant
increase
not be predictable
become zero
remain constant
Acceleration results from a change in velocity. Despite the speed remaining constant, velocity is a vector quantity and will change if the car changes direction. In rounding the turn, there is a change in the direction of the velocity, but not in the magnitude. This change in direction causes a non-zero acceleration.
The acceleration will remain equal to the equation for centripetal acceleration:
As long as the magnitude of the velocity and the radius of the turn do not change, the acceleration will remain constant.
Example Question #11 : Understanding The Relationship Between Force And Acceleration
An object moves forward with a constant velocity. What additional information do we need to know to determine the force acting upon the object?
The time the object is in motion
The force is
The mass of the object
The velocity of the object
The distance the object travels
The force is
Force is given by the product of mass and acceleration. If an object has a constant velocity, then it has no acceleration.
If an object has no acceleration, then it must also have no net force.
No additional information is needed to solve this question.
Example Question #12 : Understanding The Relationship Between Force And Acceleration
A box slides along the floor with a constant velocity. What is the net force on the box?
Since the object is moving with a constant velocity, it has no acceleration. Acceleration is only produced by a change in the velocity.
If acceleration is zero, no force is produced. This conclusion comes from Newton's second law:
Since the acceleration is zero:
Example Question #12 : Understanding The Relationship Between Force And Acceleration
A constant force acts on an object, causing it to accelerate along a track, when it suddenly breaks in half. What is the ratio of the initial acceleration of the object to the acceleration of one piece after it breaks if the force remains constant after the break?
Newton's second law states that:
We are told that the force on the object remains constant, even after it breaks in half. The mass of the broken piece will be equal to half the mass of the total object.
Using these values, we can set up equations for the initial and final accelerations.
If the force remains constant while the mass is cut in half, the acceleration of the object will double. The ratio of the new acceleration to the old acceleration will be 2:1. If the question asked for the ratio of the old acceleration to the new one, it would be 1:2.
Certified Tutor
Certified Tutor