A particle of mass m is moving in a horizontal circle of radius r under a centripetal force equal to –K/r2, where K is a constant. The total energy of the particle is
Here
∴ K.E.
Total energy
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A particle of mass m is moving in a horizontal circle of radius r under a centripetal force equal to –K/r2, where K is a constant. The total energy of the particle is
Here
∴ K.E.
Total energy
The displacement x of a particle moving in one dimension under the action of a constant force is related to the time t by the equation , where x is in meters and t is in seconds. The work done by the force in the first 6 seconds is
⇒
at ; and at ,
so, change in kinetic energy
A force (where K is a positive constant) acts on a particle moving in the xy-plane. Starting from the origin, the particle is taken along the positive x-axis to the point (a, 0) and then parallel to the y-axis to the point (a, a). The total work done by the force F on the particles is
While moving from (0,0) to (a,0)
Along positive x-axis, y = 0
i.e. force is in negative y-direction while displacement is in positive x-direction.
∴ W1 = 0
Because force is perpendicular to displacement
Then particle moves from (a, 0) to (a, a) along a line parallel to y-axis (x = +a) during this
The first component of force, will not contribute any work because this component is along negative x-direction while displacement is in positive y-direction (a,0) to (a,a). The second component of force i.e. will perform negative work
∴ =
So net work done on the particle W = W1 + W2
=
If g is the acceleration due to gravity on the earth's surface, the gain in the potential energy of an object of mass m raised from the surface of earth to a height equal to the radius of the earth R, is
Gain in potential energy
If h = R then
A lorry and a car moving with the same K.E. are brought to rest by applying the same retarding force, then
⇒
If lorry and car both possess same kinetic energy and retarding force is also equal then both come to rest in the same distance.
A particle free to move along the x-axis has potential energy given by for , where k is a positive constant of appropriate dimensions. Then
Potential energy of the particle
Force on particle
F
For small displacement
⇒ i.e. motion is simple harmonic motion.
The kinetic energy acquired by a mass m in travelling a certain distance d starting from rest under the action of a constant force is directly proportional to
Kinetic energy acquired by the body
= Force applied on it × Distance covered by the body
K.E. = F × d
If F and d both are same then K.E. acquired by the body will be same
A body is moving along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to
⇒
⇒ ⇒
Now
∴ ⇒
A particle moves from a point to when a force of N is applied. How much work has been done by the force?
Displacement of the particle,
Force on the particle,
A body of mass 1 kg begins to move under the action of a time dependent force N, where and are unit vectors along X and Y axis, What power will be developed by the force at the time (t) ?
(c) According to question, a body of mass 1kg begins to move under the action of time dependent force,
where and are unit vectors along X and Y axis
...(i)
integrating both sides, we get
Power developed by the force at the time t will be given by as
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