Physics - Online Test
Q1. Neglecting air resistance, in which of the following cases the net force acting on a stone of mass 0.1 kg is not acting downward?
Answer : Option C
Explaination / Solution:
Weight of the stone is balanced by the reaction of the floor. The only acceleration is provided by the horizontal motion of the train.
a = 1ms-2
force in horizontal direction
F = ma = 0.1 x 1 = 0.1N
Q2. Model in physics refers
Answer : Option D
Explaination / Solution:
A model is a representation of something that is often too difficult (or impossible) to display directly. While a model's design is justified using experimental information, it is only accurate under limited situations. An example is the commonly used "planetary model" of the atom, in which electrons are pictured as orbiting the nucleus, analogous to the way planets orbit the Sun. We cannot observe electron orbits directly, but the mental image helps explain the observations we can make, such as the emission of light from hot gases. Physicists use models for a variety of purposes.
Q3. The dielectric constant K of an insulator cannot be
Answer : Option A
Explaination / Solution:
Dielectric constant of a metal is infinity, and this is why the electric field inside a metal is zero. All other substances have a dielectric constant with values less than infinity but greater than 1.
Q4. The radius of gyration of a circular loop of radius r and mass m rotating about its diameter as axis is
Answer : Option C
Explaination / Solution:
Moment of inertia of ring or circular loop about axis passing through centre of mass and perpendicular to plane is MR2 ,
Applying perpendicular axis theorm
Here I = Moment of inertia about axis passing through diameter
As moment of inertia in terms of radius of gyration (k) is Mk2
I = Mk2
Q5. Capillary Rise of water is explained by
Answer : Option C
Explaination / Solution:
Capillary action(sometimes capillarity or wicking) is the ability of a liquid to flow in narrow spaces without the assistance of,or even in opposition to, external forces like gravity. The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in porous materials such as paper and plaster, in some non-porous materials such as sand and liquefied carbon fiber, or in a cell. It occurs because of intermolecular forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container wall act to propel the liquid.
Q6. Estimate the average thermal energy of a helium atom at room temperature (27 C)
Answer : Option D
Explaination / Solution:
k = boltzman constant
Q7. An equi-convex thin lens (μ =1.5) of focal length in air as 30cm is sealed into an opening in one end of tank filled with water ((μ =1.33). At the end of the tank opposite the lens is a plane mirror, 80 cm distant from the lens. The position of the image formed by the lens-water-mirror system of a small object outside the tank on the lens axis and 90cm to the left of the lens will be
Answer : Option D
Explaination / Solution:
No Explaination.
Q8. Which rays are not deflected in electric and magnetic fields?
Answer : Option B
Explaination / Solution:
No Explaination.
Q9. The average kinetic energy of the molecules in a substance is most closely associated with
Answer : Option D
Explaination / Solution:
E=32kT
Q10. A long straight wire carries an electric current of 2 A. The magnetic induction at a perpendicular distance of 5 m from the wire is
()
Answer : Option B
Explaination / Solution:
