The a is in a direction tangent to the circle, so its the tangential acceleration. This acceleration involves a speeding up or slowing down of an object as it moves along a circular path, and is equal to zero for uniform circular motion. There are equivalent questions for velocity and acceleration. Instead of asking how much distance has been covered, we sometimes ask how much of an angle something has spun through. T = the period, the time to go around onceĪs in straight-line motion, the relationship between a and v is the same as that between v and r:įor motion on circular paths it can be useful to describe motion using angular variables. If the string is released there is no force to deflect the path of the ball, so it will continue in a straight line, following path 2. If the string is released when the ball is at the position shown, which path will the ball follow? Yes - the velocity changes because its direction changes.Ī ball is being whirled in a circle. R 1 and R 2 are reactions from plane, and from Newton's law they are equal to the weights of respective blocks.įBD (6) : Draw FBD where one of the block is resting on an inclined plane and rope goes over a frictionless massless pulley (Figure given below).Uniform circular motion: motion in a circular path at constant speed. Suppose T is tension in the string, then by cutting it at 1-1' and 2-2' we can draw FBD's as shown in figure shown below.
#Circular motion body diagrams free
So tension t is responsible for dragging mass of block.Ĭaution : What happens if rope is not massless?įBD (5) : Draw free body in case of system shown (figure shown below). Since t, and T are oppositely directed their sum will come out to be zero). (We join it again then net force should become zero at that point. Let us cut it (imagine) at then the situation is as shown in figure shown below. Here string is acting as a force transmitting element įBD (4) : Suppose situations is as shown in figure above that a light inextensible string pulls a block of mass M on a frictionless rigid surface. Now a question comes Can 'R' have a direction opposite to what is shown here? Answer is, of course it can have,
Where R is reaction from the surface (R = Mg)įBD (3) : Draw free body diagrams of both the blocks (figure 1.13 a), Assuming a reaction of magnitude 'R' is present at the interface. That is why, it is stationary on the surface.įBD (2) : Draw the free body diagram of the block shown in figure 1.12. So, here itself from FBD we can see that net external force on the block is zero. R2 = mg through its centre (since the body is symmetric). mg which is the weight of the block, and is acting on the surface. There are only two forces in the system in figure above. Let us draw FBD for various given systemsįBD (1) : Block of mass M is resting on a frictionless rigid surface The diagram thus obtained is called a free body diagram.
These are called mutual interaction forces (one of this type we have seen in the illustration of IIIrd law) and show all possible acceleration. Now separate them from others by cutting the string contacts (sort of imaginary separation) In effect, make them free (that's where comes the name free body) from other components and at the same time show all the forces acting on it, external as well as internal, arising due to separation from other parts. acceleration, velocity.Ĭoming to actual situation one should first identify all the component involved in the system, say mass m 1, mass m 2 ., pulley 1, pulley 2, etc.
Now each system is ready to get treatment of laws of motion e.g. By all forces we mean external as well as internal forces (internal forces refer to mutual reactions). Whenever one attempts a problem involving forces and acceleration (say of dynamics or statics) one must show all forces and acceleration (possible acceleration may be unknown also) on each part of the system treating that part separately (it is called dividing system into possible subsystems). It is to be noticed here that during previous examples, we were using a concept called FBD implicitly which can now be brought to you conscious attention.
#Circular motion body diagrams how to
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