All AP Physics 1 Resources
Example Questions
Example Question #711 : Newtonian Mechanics
An object is attached to a spring, and is stretched 3m. If the restoring force is equal to , what is the spring constant?
Hooke's law states that the spring force is equal to the product of the spring constant and the displacement of the spring:
The force is negative because it acts in the direction opposite of the displacement from the equilibrium position (i.e. when we stretch we do so in the positive direction). We are given the force and the displacement, so we just solve for k:
Example Question #11 : Spring Force
What is the spring constant of a spring that requires an applied force of to displace its attached object by ?
This question is giving us the amount of force needed to displace an object attached to a spring, and is asking us to calculate the spring constant. Thus, we will need to make use of Hooke's law.
The above equation, Hooke's law, tells us that the restoring force of the spring is related to the displacement of the attached object. It's important to note that in the question stem, we are told that an external force of is needed to displace this object. Thus, the restoring force of the spring, due to Newton's third law, has the same magniture of the applied force but in the opposite direction. Thus, the restoring force of the spring is equal to . Plugging this value into Hooke's law, as well as the displacement of , yields:
Example Question #11 : Spring Force
An upright spring of rest length is compressed by a mass of . Determine the spring constant.
Where is the spring constant
is the compression of the spring
is the mass of the object.
is the gravity constant, which will be treated as a negative number.
Solve for :
Plug in values:
Example Question #143 : Forces
Two springs are used in parallel to suspend a mass of motionless from a ceiling. They both have rest length . However, one has a spring constant twice that of the other. The springs each have a length of while suspending the mass. Determine the spring constant of the stiffer spring.
None of these
Where and are the respective spring constants, is the stretch length, and is the gravity constant, which is a negative as the vector is pointing down.
Since
Substitute and plug in values:
Solving for :
Example Question #11 : Spring Force
A helicopter uses a rest length spring to pull up a submarine. The upward acceleration is . The spring stretches to a length of . Determine the spring constant.
Determine the net forces on the submarine:
Plug in values:
Determine what forces are acting on the submarine:
Plug in values
*Note: Acceleration due to gravity is going down so it is a negative
Solve for :
Example Question #14 : Spring Force
Two identical, massless, springs are placed in series. A mass of is hung from them. After all oscillations have stopped, the total length is . Calculate the spring constant of an individual spring.
Each spring will be subject to the same force, and since they have the same spring constant, stretch the same amount. Thus:
Total stretch:
Stretch of one spring:
Use Hooke's law:
The force will be equal to the force of gravity on the mass:
Solve for :
Example Question #12 : Spring Force
A narrow spring is placed inside a wider spring of the same length. The spring constant of the wider spring is twice that of the narrow spring. The two-spring-system is used to hold up a box of mass . They compress by .
How would much would these stretch if instead both springs were used to attach a box of mass to the ceiling?
The force of the spring in relationship to strain is independent of direction. Thus, the same force pulling on the spring would result in an equal amount of length change, albeit by stretching instead of compressing.
Example Question #12 : Spring Force
A narrow spring is placed inside a wider spring of the same length. The spring constant of the wider spring is twice that of the narrow spring. The two-spring-system is used to hold up a box of mass . They compress by .
What would the compression be if the mass were instead ?
In this problem the "spring within a spring" can be treated as a single spring.
Use Hooke's law:
Plug in values:
Solve for .
Again use Hooke's Law:
Plug in values:
Solve for
Example Question #14 : Spring Force
A narrow spring is placed inside a wider spring of the same length. The spring constant of the wider spring is twice that of the narrow spring. The two-spring-system is used to hold up a box of mass . They compress by .
What is the spring constant of the combined system?
In this problem the "spring within a spring" can be treated as a single spring.
Use Hooke's law:
Plug in values and solve for the spring constant:
Example Question #16 : Spring Force
A narrow spring is placed inside a wider spring of the same length. The spring constant of the wider spring is twice that of the narrow spring. The two-spring-system is used to hold up a box of mass . They compress by .
Determine the potential energy being stored in the springs.
In this problem the "spring within a spring" can be treated as a single spring.
Use Hooke's law:
Convert to meters and plug in values:
Solve for
Use the equation for the potential energy stored in a spring:
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