Math  /  Algebra

QuestionKinetic energy varies jointly as the mass and the square of the velocity. A mass of 6 grams and velocity of 3 centimeters per second has a kinetic energy of 27 ergs. Find the kinetic energy for a mass of 2 grams and velocity of 6 centimeters per second.
A mass of 2 grams and velocity of 6 centimeters per second has a kinetic energy of \boxed{} ergs.

Studdy Solution

STEP 1

What is this asking? If we know the kinetic energy of a moving object with a certain mass and speed, can we figure out the kinetic energy of another object with a different mass and speed, assuming kinetic energy, mass, and speed are related in a specific way? Watch out! Don't forget to square the velocity!
It's a common mistake to miss that little detail.
Also, "varies jointly" has a specific mathematical meaning, so let's make sure we understand what that means!

STEP 2

1. Define the relationship
2. Find the constant of proportionality
3. Calculate the new kinetic energy

STEP 3

Alright, so "kinetic energy varies jointly as the mass and the square of the velocity." What does *that* even mean?! It means kinetic energy is *directly proportional* to both the mass and the square of the velocity.
In simpler terms, if one goes up, the others go up too!

STEP 4

Mathematically, we can write this relationship as: KE=kmv2 KE = k \cdot m \cdot v^2 Where KEKE is the **kinetic energy**, mm is the **mass**, vv is the **velocity**, and kk is our mysterious **constant of proportionality**.
We gotta find *that* guy!

STEP 5

We're given that a mass of **6 grams** and a velocity of **3 centimeters per second** results in a kinetic energy of **27 ergs**.
Let's plug those values into our formula: 27=k632 27 = k \cdot 6 \cdot 3^2

STEP 6

Now, let's simplify and solve for kk: 27=k69 27 = k \cdot 6 \cdot 9 27=k54 27 = k \cdot 54 To isolate kk, we divide both sides by 54: 2754=k5454 \frac{27}{54} = \frac{k \cdot 54}{54} 12=k \frac{1}{2} = k So, our **constant of proportionality**, kk, is 12\frac{1}{2}!

STEP 7

Now that we know k=12k = \frac{1}{2}, we can use our formula to find the kinetic energy for a mass of **2 grams** and a velocity of **6 centimeters per second**: KE=12mv2 KE = \frac{1}{2} \cdot m \cdot v^2 KE=12262 KE = \frac{1}{2} \cdot 2 \cdot 6^2

STEP 8

Let's crunch those numbers: KE=12236 KE = \frac{1}{2} \cdot 2 \cdot 36 KE=136 KE = 1 \cdot 36 KE=36 KE = 36 Boom! The kinetic energy is **36 ergs**!

STEP 9

The kinetic energy for a mass of 2 grams and velocity of 6 centimeters per second is 36 ergs.

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