# A rebound and kinetic energy problem with a little specific heat

• redsmithers91
In summary, the conversation discusses a ball being thrown vertically downward with a speed of 15m/s and then bouncing to a maximum height of 5 meters. The questions ask about the speed of the ball after rebounding, the fraction of kinetic energy lost during the bounce, and the temperature increase of the ball if all the lost energy is absorbed. The suggested solution involves using the law of conservation of energy and the equations for kinetic and potential energy to determine the loss of energy and its relation to the ball's mass and temperature change.
redsmithers91

## Homework Statement

A ball is thrown vertically downward strikes a surface with a speed of 15m/s. It then bounces, and reaches a maximum height of 5 meters. Neglect air resistance on the ball.

a) What is the speed of the ball immediately after it rebounds from the surface?
b)What fraction of the ball's initial kinetic energy is apparently lost during the bounce?
c)If the specific heat of the ball is 1,800 j/kg*C, and if all of the lost energy is absorbed by the molecules of the ball, by how much does the temperature of the ball increase?

KE=1/2mv^2
Q=mL(delta "T")

## The Attempt at a Solution

my answer for a was crazy so i am pretty much stuck with the rest

Use law of conservation of energy - at any level (when there are no energy loss) potential energy+kinetic energy = constant. When ball is hitting a surface at 15 m/s, there is only a kinetic energy. When it reaches maximum height 5 m - there is only potential energy. Calculate what height would it be if all of kinetic energy at start where converted to potential. From difference you will find loss of energy during contact with surface ;] hope this will help. By the way - potential energy equation near Earth's surface: EP = mgh

but how do i find the mass ...i found the the joules lost to be 63(mass) joules

Well i don't know ;] so maybe express your answer as a function of mass, deltaT=(some number)/m.

## 1. What is rebound in physics?

Rebound, also known as elastic collision, is a type of collision in which the objects involved bounce off each other without permanently deforming or losing energy. This is in contrast to an inelastic collision where the objects stick together or deform after the collision.

## 2. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is calculated as 1/2 times the mass of the object times its velocity squared. Kinetic energy is a scalar quantity and is measured in joules (J).

## 3. How is kinetic energy related to rebound?

In a rebound or elastic collision, the kinetic energy of the objects before and after the collision is the same. This means that the total kinetic energy of the system is conserved, but the objects may exchange kinetic energy with each other during the collision.

## 4. What is specific heat in thermodynamics?

Specific heat, also known as specific heat capacity, is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. It is a measure of how much energy is needed to change the temperature of a substance.

## 5. How does specific heat affect a rebound and kinetic energy problem?

Specific heat is a property that describes how much heat energy is needed to change the temperature of a substance. In a rebound and kinetic energy problem, specific heat may be important in determining the final temperature of the objects after the collision, as some of the kinetic energy may be converted into heat energy. It can also affect the overall energy exchange in the collision.

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