When a body moves with a constant speed along a circle
When speed is constant in circular motion, it means work done by centripetal force is zero.
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When a body moves with a constant speed along a circle
When speed is constant in circular motion, it means work done by centripetal force is zero.
A sphere of mass m is tied to end of a string of length l and rotated through the other end along a horizontal circular path with speed v. The work done by centripetal force in full horizontal circle is
Work done by centripetal force in uniform circular motion is always equal to zero.
A ball is suspended by a thread of length l. What minimum horizontal velocity has to be imparted to the ball for it to reach the height of the suspension:
To reach the height of suspension l, the particle must have a vertical component of velocity √(2gl) at the highest point. This vertical velocity can be obtained by imparting a horizontal velocity √(2gl) at the lowest point, as the total velocity is √(2) times the horizontal component.
A body of mass m hangs at one end of a string of length l, the other end of which is fixed. It is given a horizontal velocity so that the string would just reach where it makes an angle of 60° with the vertical. The tension in the string at mean position is
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
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