One end of a string of length l is connected to a particle of mass ‘m’ and the other end is connected to a small peg on a smooth horizontal table. If the particle moves in circle with speed ‘v’, the net force on the particle (directed towards centre) will be (T represents the tension in the string)

• T

• 
• 

• zero

The x and y coordinates of the particle at any time are x = 5t – 2t² and y = 10t respectively, where x and y are in meters and t in seconds. The acceleration of the particle at t = 2 s is

• 0

• 5 m/s²

• -4 m/s²

• –8 m/s²

Suppose the charge of a proton and an electron differ slightly. One of them is –e, the other is (e + Δe). If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then Δe is of the order of [Given mass of hydrogen
mh = 1.67 × 10^–27 kg]

• 10^–20 C

• 10^–23 C

• 10^–37 C

• 10^–47 C

The diagrams below show regions of equipotentials

A positive charge is moved from A to B in each diagram.

• Maximum work is required to move q in figure (c).

• In all the four cases the work done is the same.

• Minimum work is required to move q in figure (a).

• Maximum work is required to move q in figure (b).

The physical quantity of the dimensions of length that can be formed out of c, G and e/4πε0 is [c is the velocity of light, G is the universal constant of gravitation and e is charge]

• 
• 
• 
• 

A.