There are two forms of energy related to the motion of a body: potential energy and kinetic energy. The first is that possessed by one object in relation to the position of a second object. For example, being on top of a hill will have much more potential energy available than when you are standing on your feet. The second, on the other hand, is that possessed by a body or an object when it is in motion. Kinetic energy can be impressed by a vibration, a rotation or a translation (movement of a body from one point to another). Determining the kinetic energy possessed by any body is very simple and can be done using the equation that relates the mass and speed of that body.
Steps
Part 1 of 3: Understanding Kinetic Energy
Step 1. Know the formula for calculating kinetic energy
The equation for calculating the kinetic energy (KE) is as follows: KE = 0.5 x mv2. In this formula m represents the mass of the body in question, that is the quantity of matter that constitutes it, while v is the speed at which it moves or, in other words, the speed with which its position changes.
The solution to your problem should always be expressed in joules (J), the standard unit of measurement for kinetic energy measurement. A joule, dimensionally, is represented in the following way: kg * m2/ s2.
Step 2. Determine the mass of the object
If you are struggling with solving a problem where the mass of the body in question is not known, you need to determine that magnitude yourself. You can do this by simply weighing the object in question with a normal scale. Remember that mass is a quantity expressed in kilograms (kg).
- Tare the scales. Before proceeding with the weighing of the object, you must tare the scale to the value 0. Resetting the measuring scale of a scale means "tare" the device.
- Place the object to be weighed on the weighing pan. Place it gently on the scale and take note of its weight in kilograms (kg).
- If necessary, convert grams to kilograms. To perform the final calculation, the mass must necessarily be expressed in kilograms.
Step 3. Calculate the speed at which the object is moving
Often this information will be provided to you by the text of the problem. If not, you can calculate the speed of an object using the distance traveled and the time it took to cover that space. The unit of measure used to express speed is meters per second (m / s).
- The velocity is defined by the following equation: V = d / t. Velocity is a vector quantity, which means that it has an intensity and a direction. The intensity is the value that quantifies the speed of movement, while the direction indicates the direction in which the acceleration takes place.
- For example, an object can move at a speed of 80 m / s or -80 m / s depending on the direction taken by the movement.
- To calculate the speed, you simply divide the distance traveled by the object by the time it took to travel it.
Part 2 of 3: Calculating Kinetic Energy
Step 1. Write down the relevant equation
The equation for calculating the kinetic energy (KE) is as follows: KE = 0.5 x mv2. In this formula m represents the mass of the body in question, that is the quantity of matter that constitutes it, while v is the speed at which it moves or, in other words, the speed with which its position changes.
The solution to your problem should always be expressed in joules (J), the standard unit of measurement for kinetic energy measurement. A joule, dimensionally, is represented in the following way: kg * m2/ s2.
Step 2. Enter mass and velocity values into the formula
If you don't know the mass and velocity values for the object you are studying, you need to calculate them. In our case we assume we know both these values and proceed to solve the following problem: Determine the kinetic energy of a 55 kg woman running at a speed of 3.77m / s. Since we know both the mass and the speed with which the woman moves, we can proceed to the calculation of the kinetic energy using the formula and the known values:
- KE = 0.5 x mv2
- KE = 0.5 x 55 x (3.77)2
Step 3. Solve the equation
After entering the known mass and velocity values into the formula, you can proceed to calculate the kinetic energy (KE). Square the speed, then multiply the result by all the other variables in play. Remember that the solution to the problem must be expressed in joules (J).
- KE = 0.5 x 55 x (3.77)2
- KE = 0.5 x 55 x 14.97
- KE = 411, 675 J
Part 3 of 3: Using Kinetic Energy to Calculate Speed and Mass
Step 1. Write the formula to use
The equation for calculating the kinetic energy (KE) is as follows: KE = 0.5 x mv2. In this formula m represents the mass of the body in question, that is the quantity of matter that constitutes it, while v is the speed at which it moves or, in other words, the speed with which its position changes.
The solution to your problem should always be expressed in joules (J), the standard unit of measurement for kinetic energy measurement. A joule, dimensionally, is represented in the following way: kg * m2/ s2.
Step 2. Replace the values of known variables
In solving some problems the values of kinetic energy and mass or kinetic energy and velocity may be known. The first step to solve the problem therefore consists in inserting in the formula all the values of the variables already known.
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Example 1. What is the speed at which an object with a mass of 30 kg and a kinetic energy of 500 J moves?
- KE = 0.5 x mv2
- 500 J = 0.5 x 30 x v2
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Example 2. What is the mass of an object moving at a speed of 5 m / s with a kinetic energy of 100 J?
- KE = 0.5 x mv2
- 100 J = 0.5 x m x 52
Calculate Kinetic Energy Step 9 Step 3. Set the equation to solve it based on the unknown variable
To do this, he uses the notions of algebra by resetting the equation in question, so that the known variables are all within the same member.
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Example 1. What is the speed at which an object with a mass of 30 kg and a kinetic energy of 500 J moves?
- KE = 0.5 x mv2
- 500 J = 0.5 x 30 x v2
- Multiply the mass by the coefficient 0, 5: 0, 5 x 30 = 15
- Divide the kinetic energy by the result: 500/15 = 33.33
- Calculate the square root to get the speed: 5.77 m / s
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Example 2. What is the mass of an object moving at a speed of 5 m / s with a kinetic energy of 100 J?
- KE = 0.5 x mv2
- 100 J = 0.5 x m x 52
- Calculate the square of the speed: 52 = 25
- Multiply the result obtained by the coefficient 0, 5: 0, 5 x 25 = 12, 5
- Divide the kinetic energy by the result: 100/12, 5 = 8 kg
