Work Energy and...

Two particles A and B having mass m each and charge $$q_1$$ and $$-q_2$$ respectively, are connected at the ends of a non conducting flexible and inextensible string of the length l. The particle A is fixed and B is whirled along a vertical circle with centre at A. If a vertically upward electric field of strength E exists in the space, then for minimum velocity of particle B:

A constant force of $$5N$$ is applied on a block of mass $$20\ kg$$ for a distance of $$2.0\ m$$, the kinetic energy acquired by the block is

Two perfectly elastic objects $$A$$ and $$B$$ of identical mass are moving with velocities $$15\ m/s$$ and $$10\ m/s$$ respectively collide along the direction of line joining them. Their velocities after collision are respectively:

A heavy stone hanging from a massless string of length $$15$$m is projected horizontally with speed $$147$$ m/s. The speed of the particle at the point where the tension in the string equals the weight of the particle is?

A block of mass $$1\,kg$$ is free to move along the X-axis. It is at rest and from time  $$t=0$$ onwards it is subjected to a time-dependent force $$F(t )$$ in the X-direction. The force $$F(t )$$ varies with $$t$$ as shown in figure. The kinetic energy of the block at $$t=4s$$ is

When a man increases his speed by $$2 m/s$$, he finds that his kinetic energy is doubled, the original speed of the man is

After how much time collision between the blocks will not take place practically:

A body is falling a height $$h$$. After it has fallen a height $$\dfrac{h}{2}$$. it will possess

Four alternatives are given to each of the following incomplete statements/questions. Choose the right answer:
Which of the following object has higher potential energy?

A force $$ F = K(yi + xj ) $$ ( 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