The kinetic energy k of a particle moving along a circle of radius R depends on the distance covered s as k = as2 where a is a constant. The force acting on the particle is
According to the given problem,
So,
Furthermore, as
So,
Hence
∴
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The kinetic energy k of a particle moving along a circle of radius R depends on the distance covered s as k = as2 where a is a constant. The force acting on the particle is
According to the given problem,
So,
Furthermore, as
So,
Hence
∴
A stone of mass 1 kg tied to a light inextensible string of length is whirling in a circular path of radius L in a vertical plane. If the ratio of the maximum tension in the string to the minimum tension in the string is 4 and if g is taken to be 10 m/sec2, the speed of the stone at the highest point of the circle is
Since the maximum tension TB in the string moving in the vertical circle is at the bottom and minimum tension TT is at the top.
∴ and
∴ or
or (1)
Put it in equation (1):
∴ ⇒
∴ or vT = 10 m/sec
A stone tied to a string of length L is whirled in a vertical circle with the other end of the string at the centre. At a certain instant of time, the stone is at its lowest position and has a speed u. The magnitude of the change in its velocity as it reaches a position where the string is horizontal is:
Using conservation of energy :
⇒
The driver of a car travelling at velocity v suddenly see a broad wall in front of him at a distance d. He should
When driver applies brakes and the car covers distance x before coming to rest, under the effect of retarding force F
then ⇒
But when he takes turn then ⇒
It is clear that x = r/2
i.e. by the same retarding force the car can be stopped in a less distance if the driver apply breaks. This retarding force is actually a friction force.
Work done by a frictional force is
Work done by friction can be positive, negative and zero depending upon the situation.
A block of mass 50 kg slides over a horizontal distance of 1 m. If the coefficient of friction between their surfaces is 0.2, then work done against friction is
A body of mass m is moving in a circle of radius r with a constant speed v. The force on the body is and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle
Work done by centripetal force is always zero, because force and instantaneous displacement are always perpendicular.
A man pushes a wall and fails to displace it. He does
No displacement is there.
A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joules, the angle which the force makes with the direction of motion of the body is
⇒
⇒
A force acts on a 30 gm particle in such a way that the position of the particle as a function of time is given by , where x is in metres and t is in seconds. The work done during the first 4 seconds is
∴ and
(According to work energy theorem)
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