PRACTICE IT Use the worked example above to help you solve this problem. A 49.7 kg circus acrobat drops from a height of 1.57 meters straight down onto a springboard with a force constant of 6.90 x 10³ N/m, as shown in the figure. By what maximum distance does she compress the spring? m EXERCISE HINTS: GETTING STARTED II'M STUCK! An 6.37 kg block drops straight down from a height of 0.77 m, striking a platform spring having a force constant of 9.50 x 10² N/m. Find the maximum compression of the spring. m
Kinematics
A machine is a device that accepts energy in some available form and utilizes it to do a type of work. Energy, work, or power has to be transferred from one mechanical part to another to run a machine. While the transfer of energy between two machine parts, those two parts experience a relative motion with each other. Studying such relative motions is termed kinematics.
Kinetic Energy and Work-Energy Theorem
In physics, work is the product of the net force in direction of the displacement and the magnitude of this displacement or it can also be defined as the energy transfer of an object when it is moved for a distance due to the forces acting on it in the direction of displacement and perpendicular to the displacement which is called the normal force. Energy is the capacity of any object doing work. The SI unit of work is joule and energy is Joule. This principle follows the second law of Newton's law of motion where the net force causes the acceleration of an object. The force of gravity which is downward force and the normal force acting on an object which is perpendicular to the object are equal in magnitude but opposite to the direction, so while determining the net force, these two components cancel out. The net force is the horizontal component of the force and in our explanation, we consider everything as frictionless surface since friction should also be calculated while called the work-energy component of the object. The two most basics of energy classification are potential energy and kinetic energy. There are various kinds of kinetic energy like chemical, mechanical, thermal, nuclear, electrical, radiant energy, and so on. The work is done when there is a change in energy and it mainly depends on the application of force and movement of the object. Let us say how much work is needed to lift a 5kg ball 5m high. Work is mathematically represented as Force ×Displacement. So it will be 5kg times the gravitational constant on earth and the distance moved by the object. Wnet=Fnet times Displacement.
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**REMARKS**
The other solution, \( d = -0.437 \, \text{m} \), can be rejected because \( d \) was chosen to be a positive number at the outset. A change in the acrobat's center of mass, say, by crouching as she makes contact with the springboard, also affects the spring's compression, but that effect was neglected. Shock absorbers often involve springs, and this example illustrates how they work. The spring action of a shock absorber turns a dangerous jolt into a smooth deceleration, as excess kinetic energy is converted to spring potential energy.
**QUESTION**
Is it possible for the acrobat to rebound to a height greater than her initial height? Explain.
(Select all that apply.)
- □ No. The kinetic energy that the acrobat gains on the way down is converted entirely back into potential energy when she reaches the initial height.
- □ Yes. The acrobat can provide mechanical energy by pushing herself up while in contact with the springboard.
- □ Yes. Elastic energy is always present in the spring and can give the acrobat greater height than initially.
- □ Yes. The acrobat can bend her knees while falling and then straighten them as if jumping when bouncing upward again.
- □ No. There is no external source of energy to provide the potential energy at a greater height.
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**PRACTICE IT**
Use the worked example above to help you solve this problem. A \( 49.7 \, \text{kg} \) circus acrobat drops from a height of \( 1.57 \, \text{meters} \) straight down onto a springboard with a force constant of \( 6.90 \times 10^3 \, \text{N/m} \), as shown in the figure. By what maximum distance does she compress the spring?
\[\underline{\hphantom{mm}} \, \text{m}\]
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**EXERCISE**
**HINTS:** [GETTING STARTED](#) | [I'M STUCK!](#)
An \( 6.37 \, \text{kg} \) block drops straight down from a height of \( 0.77 \, \text{m} \), striking a platform spring having a force constant of \( 9.50 \times 10^2 \, \text{](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1a2be487-a4f1-4704-8a71-b11163658c73%2F53a52efa-5ba6-415b-a9d5-dd01ef942bc0%2Fbvwr7e7_processed.png&w=3840&q=75)
![# Example 5.10: Circus Acrobat
### Goal
Use conservation of mechanical energy to solve a one-dimensional problem involving gravitational potential energy and spring potential energy.
### Problem
A 50.0 kg circus acrobat drops from a height of 2.00 meters straight down onto a springboard with a force constant of 8.00 x 10³ N/m, as shown in the figure. By what maximum distance does she compress the spring?
### Strategy
Nonconservative forces are absent, so conservation of mechanical energy can be applied. At the two points of interest, the acrobat's initial position and the point of maximum spring compression, her velocity is zero, so the kinetic energy terms will be zero. Choose y = 0 as the point of maximum compression, so the final gravitational potential energy is zero. This choice also means that the initial position of the acrobat is yᵢ = h + d, where h is the acrobat's initial height above the platform and d is the spring's maximum compression.
### Diagram Explanation
- **Figure (a)**: Shows an acrobat jumping onto a springboard, causing it to compress.
- **Figure (b)**: Shows the acrobat at the initial position before jumping.
### Solution
**Use conservation of mechanical energy.**
\[ (KE + PE_g + PE_s)_i = (KE + PE_g + PE_s)_f \]
The only nonzero terms are the initial gravitational potential energy and the final spring potential energy.
\[ 0 + mg(h + d) + 0 = 0 + 0 + \frac{1}{2}kd^2 \]
\[ mg(h + d) = \frac{1}{2}kd^2 \]
Substitute the given quantities and rearrange the equation into standard quadratic form.
\[ (50.0 \, \text{kg})(9.80 \, \text{m/s}^2)(2.00\, \text{m} + d) = \frac{1}{2}(8.00 \times 10^3 \, \text{N/m})d^2 \]
\[ d^2 - (0.123 \, \text{m}) \, d - 0.245 \, \text{m}^2 = 0 \]
Solve with the quadratic formula:
\[ d = 0.560 \, \text{m} \](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1a2be487-a4f1-4704-8a71-b11163658c73%2F53a52efa-5ba6-415b-a9d5-dd01ef942bc0%2Ffx4kqcj_processed.png&w=3840&q=75)

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