Physics Questions & Answers - Free Online Practice

2,486.

If relative density of a metal is 19, what will be the mass of 20cm³ of the metal when immersed in water?

380g

400g

360g

39g

180g

View answer & explanation

Correct answer is A

R.d = 19, therefore, density = 19gcm^-3

mass = velocity x density

= 20 x 19

= 380g

2,487.

The refractive index of liquid is 1.5. If the velocity of light in vacuum is 3.0 x 10⁸ms^-1, the velocity of light in the liquid is

1.5 x 10⁸m^-1

2.0 x 10⁸m^-1

3.0 x 10⁸m^-1

4.5 x 10⁸m^-1

9.0 x 10⁸m^-1

View answer & explanation

Correct answer is B

n = \(\frac{\text{speed in air}}{\text{speed in glass}}\)

1.5 = \(\frac{3\times10^4}{\text{speed in glass}}\)

speed in glass = 2 x 10⁸ms^-1

2,488.

The force with which an object is attracted to the earth is called its

acceleration

mass

gravity

impulse

weight

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

2,489.

Which of the following statements about friction is NOT correct?

The force of kinetic friction is less than the force of static friction

The force of kinetic friction between two surfaces is independent of the areas in contact provided the normal reaction is unchanged

The force of rolling friction between two surfaces is less than the force of sliding friction

The angle of friction is the angle between the normal reaction and the force of friction

Friction may be reduced by lubrication

View answer & explanation

Correct answer is D

- Static Friction is friction which is experienced when an object is placed on a surface. And, Kinetic friction is due to the movement of an object on a surface.

- Static friction is greater than kinetic friction because there are more forces at work keeping an object stationary than there are forces working to resist an object once it is in motion.

- Rolling friction is the weakest type of friction, static being the strongest. The frictional force depends on the area of contact between the two bodies. As the area of contact is less in rolling friction than the sliding friction, so rolling friction is weaker than sliding friction.

2,490.

In a resonance tube experiment, a tube fixed length is closed at one end and several tuning forks of increasing frequency used to obtain resonance at the open end. If the tuning fork with the lowest frequency which gave resonance had a frequency f1 and the next tuning fork to give resonance had a frequency f2, find the ratio \(\frac{f^2}{f^1}\).

\(\frac{1}{2}\)

\(\frac{1}{3}\)

View answer & explanation

Correct answer is B

\(\lambda_1\) = 4L1 and \(\lambda_2\) = -L1

F\(\lambda\) = velocity

F1 x \(\lambda_1\) = F2 x
\(\lambda_2\) ; F1 x 4\(\lambda_1\) = F2 x -\(\lambda_2\)

= \(\frac{F_2}{F_1}\) = 3