how do you solve K=1/2mv^2

If you are solving for "m" you would use the following formula. m = (2(K))/(v^2) If you are solving for "v" you would use this formula. v = sqrt((2(K))/(m))

Is energy scalar or vector?

It can only be a scalar because it doesn`t matter the direction it`s going, just the speed.

What is rotational kinetic energy?

consider watching this Khan video for the answer: https://www.khanacademy.org/science/ap-physics-1/ap-torque-angular-momentum/rotational-kinetic-energy-ap/v/rotational-kinetic-energy

Main content

Course: Class 11 Physics (India) - Hindi > Unit 4

Lesson 2: Kinetic energy (Hindi)

Kinetic energy review

Google Classroom

Review the key concepts, equations, and skills for kinetic energy. Understand how kinetic energy can't be negative but the change in kinetic energy can be negative.

Key terms

Term (symbol)	Meaning
Kinetic energy	Energy from translational or rotational motion. SI units of joules ( $J$ ‍).
Translational motion	Linear motion of a rigid body. SI units of $\frac{m}{s}$ ‍.
Translational kinetic energy ( $K$ ‍)	Energy due to linear motion of a rigid body. SI units of joules ( $J$ ‍).

Equations

Equation	Symbols	Meaning in words
$K = \frac{1}{2} m v^{2}$ ‍	$K$ ‍ is translational kinetic energy, $m$ ‍ is mass, and $v$ ‍ is the magnitude of the velocity (or speed)	Translational kinetic energy is directly proportional to mass and the square of the magnitude of velocity.
$Δ K = \frac{1}{2} m (v^{2} - v_{0}^{2})$ ‍	$Δ K$ ‍ is change in kinetic energy, and $v$ ‍ and $v_{0}$ ‍ are the magnitudes of the final and initial velocity	Change in kinetic energy is the difference between the final and initial kinetic energy.

Common mistakes and misconceptions

Kinetic energy can’t be negative, although the change in kinetic energy $Δ K$ ‍ can be negative. Because mass can’t be negative and the square of speed gives a non-negative number, kinetic energy can’t be negative. Either something is moving and has positive kinetic energy, or it is not moving and has zero kinetic energy. If the final speed is less than the initial speed, then the final kinetic energy is less than the initial kinetic energy and $Δ K$ ‍ is negative.
Some people think doubling speed means doubling the energy. The kinetic energy is proportional to the square of the speed, so doubling the speed increases the kinetic energy by a factor of $4$ ‍. However, doubling the speed does double the momentum, which we will cover in the next unit.

Learn more

For deeper explanations of kinetic energy, see our article on kinetic energy with worked example problems.

To check your understanding and work toward mastering these concepts, check out the exercise on using the kinetic energy equation.

Want to join the conversation?

Sort by:

BlueCreeperX
Posted 4 years ago. Direct link to BlueCreeperX's post “Is energy scalar or vecto...”
Is energy scalar or vector?
Button navigates to signup pageComment on BlueCreeperX's post “Is energy scalar or vecto...”
(2 votes)
Answer
- Plinio Bassi
  Posted 3 years ago. Direct link to Plinio Bassi's post “It can only be a scalar b...”
  It can only be a scalar because it doesnt matter the direction its going, just the speed.
  Button navigates to signup page
  (3 votes)
torymorrow
Posted 5 years ago. Direct link to torymorrow's post “how do you solve K=1/2mv^...”
how do you solve K=1/2mv^2
Button navigates to signup pageButton navigates to signup page
(3 votes)
Answer
- dkoenig
  Posted 5 years ago. Direct link to dkoenig's post “If you are solving for "m...”
  If you are solving for "m" you would use the following formula.
  m = (2(K))/(v^2)
  If you are solving for "v" you would use this formula.
  v = sqrt((2(K))/(m))
  Button navigates to signup page
  (3 votes)
s604209
Posted 3 years ago. Direct link to s604209's post “Is energy scalar or vecto...”
Is energy scalar or vector?
Button navigates to signup pageButton navigates to signup page
(2 votes)
Answer
- Inspiron13
  Posted 3 years ago. Direct link to Inspiron13's post “Do you think energy has a...”
  Do you think energy has a direction? Of course it has a direction it can flow, but given on its own, its a scalar quantity. It only has magnitude.
  
  We can think of this like mass (energy is mass but in a different form). Mass doesn't have direction, but has magnitude, so its a scalar quantity.
  Button navigates to signup page
  (1 vote)
Bhagyashree U Rao
Posted 5 years ago. Direct link to Bhagyashree U Rao's post “What is rotational kineti...”
What is rotational kinetic energy?
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- Grace3083
  Posted 5 years ago. Direct link to Grace3083's post “consider watching this Kh...”
  consider watching this Khan video for the answer:
  https://www.khanacademy.org/science/ap-physics-1/ap-torque-angular-momentum/rotational-kinetic-energy-ap/v/rotational-kinetic-energy
  Button navigates to signup page
  (3 votes)
Marley.Trench
Posted a year ago. Direct link to Marley.Trench's post “how to weight and speed e...”
how to weight and speed effect eachother?
Button navigates to signup pageButton navigates to signup page
(2 votes)
Answer
jonathan.shanks
Posted 2 years ago. Direct link to jonathan.shanks's post “why can't I get to the qu...”
why can't I get to the quiz
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
kusmungee
Posted 4 years ago. Direct link to kusmungee's post “If kinetic energy is decr...”
If kinetic energy is decreased to 25% of its original value, how does the velocity change?
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- KLaudano
  Posted 4 years ago. Direct link to KLaudano's post “KE = 1/2 * m * v^2 <==> v...”
  KE = 1/2 * m * v^2 <==> v = sqrt(2 * KE / m)
  
  v1 = sqrt(2 * KE / m) = sqrt(2) * sqrt(KE / m)
  v2 = sqrt(2 * (.25 * KE) / m) = sqrt(1/2) * sqrt(KE / m)
  
  v1 / v2 = sqrt(1/2)/sqrt(2) * sqrt(KE / m)/sqrt(KE / m)
  = sqrt(1/4)*1 = 1/2
  
  v1 = 1/2 * v2
  
  When the kinetic energy is 1/4 of the original value, the new velocity is half of the original velocity.
  Button navigates to signup page
  (1 vote)
41150
Posted a year ago. Direct link to 41150's post “how does energy not have ...”
how does energy not have a direction?
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- Luke Rieff
  Posted a year ago. Direct link to Luke Rieff's post “It indicates the energy s...”
  It indicates the energy something has. It either is something, or nothing. The energy is to the object, and doesn't have an direction because of that.
  Button navigates to signup page
  (1 vote)
ar.kunal04
Posted 2 years ago. Direct link to ar.kunal04's post “I can not figure out the ...”
I can not figure out the dependency of kinetic energy on frame of reference
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
esteeparke
Posted 3 years ago. Direct link to esteeparke's post “How do you find m like m=...”
How do you find m like m=... what
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- IsotonicFlaccidCell21
  Posted 3 years ago. Direct link to IsotonicFlaccidCell21's post “Im presuming you are tryi...”
  Im presuming you are trying to make m the subject from e=1/2 mv^2...
  then it is m=2e/(v^2)
  Comment on IsotonicFlaccidCell21's post “Im presuming you are tryi...”
  (1 vote)