An object is placed at the focus of a concave mirror. The image will be

• real, inverted, same size at the focus

• real, upright, same size at the focus

• virtual, inverted, highly enlarged at infinity

• real, inverted, highly enlarged at infinity

An optician prescribes a power = -0.5 dioptre. The corresponding lens must be a

• convex lens of focal length 2 m

• convex lens of focal length 50 cm

• concave lens of focal length 2 m

• concave lens of focal length 50 cm

A current I flows through a potential difference V in an electrical circuit containing a resistance R. The product of V and I, i.e., VI may be understood as

• resistance R

• heat generated by the circuit

• thermal power radiated by the circuit

• rate of change of resistance

A particle is moving freely. Then its

• kinetic energy is always greater than zero

• potential energy is greater than zero and kinetic energy is less than zero

• potential energy is less than zero and kinetic energy is greater than zero

• potential energy is zero and kinetic energy is less than zero

245.

The displacement of a particle at time t is given by

$\overrightarrow{\mathrm{x}}= \mathrm{a}\stackrel{\wedge }{\mathrm{i}}+ \mathrm{bt}\stackrel{\wedge }{\mathrm{j}}+ \frac{\mathrm{c}}{2}{\mathrm{t}}^2\stackrel{\wedge }{\mathrm{k}}$

where a, band care positive constants. Then the particle is

• accelerated along $\stackrel{\wedge }{k}$-direction

• decelerated along $\stackrel{\wedge }{\mathrm{k}}$-direction

• decelerated along $\stackrel{\wedge }{\mathrm{j}}$-direction

• accelerated along $\stackrel{\wedge }{\mathrm{j}}$-direction

Gravitational force shares a common feature with electromagnetic force. In hoth cases, the force is

• between massive and neutral objects

• between charged objects

• a short range

• a long range

The weight of an object may be assigned by using Newton's

• first law of motion

• second law of motion

• third law of motion

• laws of gravitation

A current of 0-5 A is drawn by a filament of an electric bulb for 20 minutes. The amount of electric charge that flows through the circuit is

• 1 C

• 10 C

• 600 C

• 300 C

Which one among the following properties of a proton may change while it moves freely in a magnetic field?

• Speed

• Charge

• Mass

• Velocity

Power required by a boy of mass 30 kg to run up a staircase of 40 steps in 10 seconds is (Height of each step is 15 cm)

(Take g = 10 m/s²)

• 1800 Watt

• 180 Watt

• 18000 Watt

• 18 Watt