Physics - Online Test
Q1. One end of a string of length l is connected to a particle of mass m and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed v, T is the tension in the string, the net force on the particle directed towards the centre is
Answer : Option A
Explaination / Solution:
According to Newton's third law of motion, the net force on a rotating particle is equal to Tension in the String. As the action (ie force towards the centre) and reaction (tension in the string) are equal in magnitude and opposite in direction.
Q2. Technology started with
Answer : Option B
Explaination / Solution:
The history of technology is the history of the invention of tools and techniques and is similar to other sides of the history of humanity. Technology can refer to methods ranging from as simple as language and stone tools to the complex genetic engineering and information technology that has emerged since the 1980s.
Q3. If one penetrates a uniformly charged metallic sphere, the electric field strength E
Answer : Option A
Explaination / Solution:
Electric field due to a solid sphere of uniform charge density at points inside the sphere varies asIt decreases at the rate However if the sphere were a hollow shell, the electric field would be zero at all points where r < R
Q4. The moment of inertia of a circular disc of mass M and radius R rotating about an axis passing through its edge and perpendicular to the plane of the disc is
Answer : Option C
Explaination / Solution:
Moment of inertia of a disc about axis passing through Centre of mass and perpendicular to plane
if I = Moment of inertia of a disc about axis passing through its edge and perpendicular to plane
applying parellal axis theorm
Q5. The excess pressure across the surface of a soap bubble of radius r(with σ as the surface tension of soap solution)is
Answer : Option B
Explaination / Solution:
No Explaination.
Q6. Estimate the average thermal energy of a helium atom the temperature of 10 million Kelvin (the typical core temperature in the case of a star).
Answer : Option C
Explaination / Solution:
k = boltzman constant
Q7. When a lens is inserted between an object & the screen which are at fixed distance apart, the size of the image is either 6cm or 2/3 cm. The size of the object is
Answer : Option A
Explaination / Solution:
No Explaination.
Q8. A radioactive element X with a half life of 2 hours decays giving a stable element Y. After a time of t hours ratio of X to Y atoms is 1:7, then the value of t is
Answer : Option A
Explaination / Solution:
No Explaination.
Q9. Which of the following is true of the Celsius and Kelvin temperature scales?
Answer : Option D
Explaination / Solution:
A Kelvin degree and a Celsius degree means change in temperature.
Q10. What should be the current in a circular coil of radius 5 cm to annul BH=5×10−5 T at the center?
Answer : Option C
Explaination / Solution:
The magnetic field produced by the coil at the centre should be equal and opposite to the The field at the centre of a circular coil .The current needed to produce a field equal to
