Kinetic Energy of a body is measured by the amount of work it does in bringing it from rest to state where its speed is v m/s.įor a body with mass m moving with speed v m/s, the kinetic energy is defined as: There are many kinds of energy but in Dynamics, we are concerned with Mechanical energy which deals with kinetic and potential energy only. Since energy of a body is measured by the work, therefore unit of energy is also Joule. The energy of a body is its capacity for doing work. Find the work done.Īs the force applied has an angle the formula will have cos ( ) The Force applied is inclined upwards by 20°. Leo applies a force of 200 N to a box to move it 5 m forward. Iv) If there are different forces, ie p, q, r etc acting on a body, then the work done by these forces in any displacement of the object is equal to the algebraic sum of the work done by p, q, r separately. Iii) If = 90°, i.e the force and the displacements are perpendicular to each other, then the work done by the force is ZERO.Ĭonversely if the work done by a force F is 0, then F and the displacement are perpendicular to each other.
Ii) Let’s suppose a force F Newton acts on a body and moves it from point A to B and F makes an angle with the direction of the displacement D.Īs shown in Fig 2, the resolved part of F along AB = F cos ( ), therefore only F cos ( ) does the work. The body covers a distance of D metres from point A to point B in the direction of the force as shown in Fig 1, then the work done by the force is equal to. I) Let F Newton be a force applied to a body. Let’s study a few different cases of work: One Joule is defined as the work done by a force of 1 Newton in moving a body a distance of 1 metre in the direction of the force.įor large amount of work, the unit used is KiloJoule (KJ) which is equivalent to 1000 Joules. When a force is applied to an object and the object covers a certain distance in the direction of the force, then the force is said to do work. Power is the rate of doing work or the work done per second.
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