Physics · Work, Energy And Power · NEET
Kinetic energy is a scalar. It only has a size (magnitude), no direction. This is because it depends on v², and squaring a speed always gives a positive number no matter which way the body moves. So a car moving north and the same car moving south at the same speed have the exact same kinetic energy. For NEET, remember: all forms of energy and work are scalars.
The ½ comes from the derivation using the work-energy theorem. Work done by a constant force is W = F s, and using v² = u² + 2as with u = 0 gives s = v²/2a. Since F = ma, the work becomes W = ma × v²/2a = ½ m v². This work stored in the moving body is its kinetic energy, so the ½ is a natural result of the maths, not a made-up number.
No. Kinetic energy can never be negative. Since KE = ½ m v², both mass m and v² are always positive or zero. The smallest possible value is zero, which happens only when the body is at rest (v = 0). If a NEET question gives you a negative answer for KE, you have made a sign or calculation mistake.
If speed is doubled, kinetic energy becomes four times larger. Because KE depends on v² (not v), multiplying v by 2 multiplies KE by 2² = 4. Similarly, tripling the speed makes KE nine times larger. This 'square' relationship is a very common trap in NEET, so always check whether the change is in speed or in mass.
A particle of mass 10 g moves along a circle of radius 6.4 cm with a constant tangential acceleration. The magnitude of this acceleration, if the kinetic energy of the particle becomes equal to 8×10⁻⁴ J by the end of the second revolution after the beginning of the motion, is
A particle is released from height S from the surface of the Earth. At a certain height its kinetic energy is three times its potential energy. The height from the surface of the Earth and the speed of the particle at that instant are respectively
The sum of the kinetic energy and potential energy of a simple pendulum bob is 0.02 J. The speed of the bob at the equilibrium position is approximately (mass of the bob = 20 g)
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The SI unit of kinetic energy is the joule (J), the same as for work and all other forms of energy. From KE = ½ m v², the unit is kg·m²/s² = J. Since energy and work share the same unit, this is a key idea for the work-energy theorem in NEET.
Kinetic energy can be written as KE = p² / (2m), where p = mv is the linear momentum. This form is very useful when a NEET question links kinetic energy and momentum. You can read more on the linked page 'Relation Between Kinetic Energy and Momentum'.
No. Kinetic energy depends only on the speed (magnitude of velocity), not on direction, because it is a scalar and uses v². A body moving left or right at the same speed has the same kinetic energy.
Kinetic energy is zero only when the object is at rest, that is when v = 0. At any non-zero speed, KE is always positive. It can never become negative.
