The position - time (x - t) graph for the motion of a body is given below

Which one among the following is depicted by the above graph?

• Positive acceleration

• Negative acceleration

• Zero acceleration

• None of the above

292.

Which one among the following waves are called waves of heat energy?

• Radio waves

• Infrared waves

• Ultraviolet waves

• Microwaves

The phenomenon of 'trade winds' takes place due to

• conduction of heat

• convection of heat

• radiation

• None of the above

Ultrasonic waves are those sound waves having a frequency

• between 20 hertz and 1000 hertz

• between 1000 hertz and 20000 hertz

• more than 20 kilohertz

• less than 20 hertz

The image formed by a convex mirror of a real object is larger than the object (u = object distance, f = focal length)

• when u < 2f

• when u>2f

• for all values of u

• for no value of u

Refractive index of an optical medium changes with

1. the nature of the medium.
2. the change in the angle of incidence of the ray.
3. colour of the incident ray.

Select the correct answer using the code given below:

• 1 and 3 only

• 2 and 3 only

• 1 and 2 only

• 1,2 and 3

A one-rupee coin is placed at the bottom of a vessel. Water is then poured into the vessel such that the depth of water becomes 20 cm. If water has refractive index 4/3, the coin would be seen at a depth of

• 20 cm

• about 26 cm

• 15 cm

• 25 cm

The momentum of a body is

1. a vector quantity.
2. a conserved quantity in an isolated system.
3. same as a force in linear motion.

Select the correct answer using the code given below:

• 1 and 3 only

• 2 and 3 only

• 1 and 2 only

• 1, 2 only

If the ratio of the weight of a man in a stationary lift and. when it is moving downwards with a uniform acceleration 'a' is 3:2, then the value of 'a' is

• 3g/2

• g/3

• g

• 2g/3

A body is thrown upward against the gravity 'g with initial velocity 'u'. Which one among the following is the correct expression for its final velocity when attains the maximum height?

• u²/(2g)

• 2g/u²

• u²g/2

• None of the above