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When an \(81.0\) - \(\mathrm{kg}\) adult uses a spiral staircase to climb to the second floor of his house, his gravitational potential energy increases by \(2.0 \times 10^{3} \mathrm{~J}\). By how much does the potential energy of an \(18.0\) - \(\mathrm{kg}\) child increase when the child climbs a normal staircase to the second floor?

Short Answer

Expert verified
The child's potential energy increases by approximately 448.9 J.

Step by step solution

01

Understand the Relationship

Gravitational potential energy (GPE) is calculated using the formula \( \Delta PE = mgh \), where \( m \) is mass, \( g \) is the gravitational acceleration \((9.8 \, \text{m/s}^2)\), and \( h \) is the height. The height \( h \) should be the same for both the adult and the child as they're climbing to the same floor.
02

Calculate Height for the Adult

We know the adult's mass \( m = 81.0 \, \text{kg} \) and his increase in potential energy \( \Delta PE = 2.0 \times 10^{3} \, \text{J} \). Solve for height: \( h = \frac{\Delta PE}{m \cdot g} = \frac{2.0 \times 10^{3}}{81.0 \cdot 9.8} \, \text{m} \).
03

Calculate Height Numerically

Substitute the known values into the equation: \[ h = \frac{2.0 \times 10^{3}}{81.0 \cdot 9.8} \approx 2.54 \, \text{m} \].
04

Calculate the Child's Potential Energy Increase Using Height

Now, use the height calculated \( h \approx 2.54 \, \text{m} \) for the child with mass \( m = 18.0 \, \text{kg} \) to find the potential energy increase: \( \Delta PE = mgh = 18.0 \cdot 9.8 \cdot 2.54 \).
05

Calculate Numerically for the Child

Perform the calculation: \( \Delta PE = 18.0 \cdot 9.8 \cdot 2.54 \approx 448.9 \, \text{J} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Conservation of Energy
The conservation of energy is a vital principle in physics, which states that energy cannot be created or destroyed in an isolated system.
Instead, it merely transforms from one form to another. In scenarios involving gravitational potential energy, such as a person climbing stairs, the mechanical energy is converted from kinetic energy when climbing, to gravitational potential energy as the person ascends.
This principle is evident when calculating the potential energy of both the adult and the child in our example.
As each climbs to the same height, the gravitational potential energy gained is proportional to their mass times the height to which they climb.
Understanding that energy is conserved allows us to predict how much potential energy the child gains, given that we know the height and the mass of the child. This principle simplifies the calculation, as we assume all energy is conserved and transformed into potential energy.
Physics Problem Solving
Solving physics problems often involves breaking down complex scenarios into manageable steps. This approach allows us to better understand the relationships between different physical quantities, like mass, height, and energy in this example.
In our exercise, by first calculating the change in potential energy for an adult using the formula \( \Delta PE = mgh \), we determined the height gained. Understanding this relationship is fundamental when solving physics problems, as it allows us to interpolate these calculations for other situations or subjects, like calculating the child's potential energy gain.
The logical process of solving problems typically includes:
  • Identifying the relevant physical laws or principles involved.
  • Breaking the problem into smaller, more manageable parts.
  • Substituting known values into the appropriate equations.
  • Performing calculations step-by-step to avoid errors.
In doing so, physics becomes simpler and more approachable, as each step builds upon the last to reach the solution.
Kinematics Calculation
Kinematics involves the study of motion of objects without considering the forces that cause this motion.
In our exercise, the height determined with kinematics calculations directly affected the potential energy change observed.The formula \( \Delta PE = mgh \) links the mass and height, assuming gravity's constant acceleration, and is primarily used here to connect the energy gain with the kinematic height climbed.
This relation illustrates that the height calculated in kinematics can influence other calculations, ensuring a consistent framework of understanding across different physical concepts.
When performing kinematics calculations:
  • Understand that height and distance travelled become crucial when defining potential energy.
  • Use kinematic equations to find specific variables when others are known.
  • Calculate consistently across problems to ensure comprehension.
In this way, kinematics serves as a bridge to understanding how physical movements impact energy and other dynamics in physics.

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Most popular questions from this chapter

A roller coaster \((375 \mathrm{~kg})\) moves from \(A(5.00 \mathrm{~m}\) above the ground) to \(B(20.0 \mathrm{~m}\) above the ground). Two nonconservative forces are present: friction does \(-2.00 \times 10^{4} \mathrm{~J}\) of work on the car, and a chain mechanism does \(+3.00 \times 10^{4} \mathrm{~J}\) of work to help the car up a long climb. What is the change in the car's kinetic energy, \(\Delta \mathrm{KE}=\mathrm{KE}_{\mathrm{f}}-\mathrm{KE}_{0}\), from \(A\) to \(B\) ?

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The cheetah is one of the fastest-accelerating animals, because it can go from rest to \(27 \mathrm{~m} / \mathrm{s}\) (about 60 \(\mathrm{mi} / \mathrm{h}\) ) in \(4.0 \mathrm{~s}\). If its mass is \(110 \mathrm{~kg}\), determine the average power developed by the cheetah during the acceleration phase of its motion. Express your answer in (a) watts and (b) horsepower.

A basketball of mass \(0.60 \mathrm{~kg}\) is dropped from rest from a height of \(1.05 \mathrm{~m}\). It rebounds to a height of \(0.57 \mathrm{~m}\) (a) How much mechanical energy was lost during the collision with the floor? (b) A basketball player dribbles the ball from a height of \(1.05 \mathrm{~m}\) by exerting a constant downward force on it for a distance of \(0.080 \mathrm{~m}\). In dribbling, the player compensates for the mechanical energy lost during each bounce. If the ball now returns to a height of 1.05 \(\mathrm{m},\) what is the magnitude of the force?

A 63 -kg skier coasts up a snow-covered hill that makes an angle of \(25^{\circ}\) with the horizontal. The initial speed of the skier is \(6.6 \mathrm{~m} / \mathrm{s}\). After coasting a distance of \(1.9 \mathrm{~m}\) up the slope, the speed of the skier is \(4.4 \mathrm{~m} / \mathrm{s}\). (a) Find the work done by the kinetic frictional force that acts on the skis. (b) What is the magnitude of the kinetic frictional force?

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