CBSE 11TH PHYSICS - Online Test
Q1. A spherical solid ball of 1 kg. mass and radius 3 cm is rotating about an axis passing through its centre with an angular velocity of 50 radians/s. The kinetic energy of rotation is
Answer : Option D
Explaination / Solution:
M=1KgR=3cm=3×10−2mω=50rad/sK=12Iω2=12×25MR2×ω2K=12×25×1×(3×10−2)2×50×50=920J
Q2. Soap helps in better cleansing of clothes because
Answer : Option B
Explaination / Solution:
Water molecules have a tendency to stick together, as opposed to losing their fellow water molecules’ company and sticking to other surfaces. This happens as a result of something known as the ‘surface tension’ of water.
Surfactants are substances that help lower the surface tension of water molecules, thus ‘persuading’ them to wet things more uniformly.
Soaps (which are a type of detergent) contain surfactants in significant amounts, which help water spread uniformly over clothes.
Q3. Air at 20.0 in the cylinder of a diesel engine is compressed from an initial pressure of 1.00 atm and volume of 800.0 to a volume of 60.0 . Assume that air behaves as an ideal gas with and that the compression is adiabatic. Find the final temperature of the air
Answer : Option C
Explaination / Solution:
T1V1γ−1=T2V2γ−1T2=T1(V1V2)γ−1=1×(80060)1.4−1=826K
Q4. The triple points of neon is 24.57 K. Express this temperatures on the Celsius and Fahrenheit scales
Answer : Option B
Explaination / Solution:
TK = 24.57K
after solving
TC = –248.58 C
TF = – 415.44 F
Q5. Which of the following is the most precise device for measuring length?
Answer : Option A
Explaination / Solution:
A device with minimum count is the most suitable to measure length.
Least count of vernier callipers = 1 standard division (SD) – 1 vernier division (VD) = cm
Least count of screw gauge = = = 0.001cm
Least count of an optical device = Wavelength of light 10–5 cm = 0.00001 cm
Hence, it can be inferred that an optical instrument is the most suitable device to measure length.
Q6. Two pendulums of length I meter and 16 meters start vibrating one behind the other from the same stand. At some instant the two are in the mean position in the same phase. The time period of shorter pendulum is T. The minimum time after which the two threads of the pendulums will be one behind the other is
Answer : Option C
Explaination / Solution:
No Explaination.
Q7. A truck is coming towards you from a distance of 1000m on a straight road. At time t=0 it starts from rest. At time t=10 seconds its velocity is 20m/s. What is the average acceleration in m/
Answer : Option A
Explaination / Solution:
Average acceleration is the change in velocity divided by an elapsed time.
Initial velocity u = 0 m/s
Final velocity v = 20 m/s
Time elapsed = 10-0 = 10 s
Average acceleration
Q8. A fork of unknown frequency when sounded with another fork of frequency 256 Hz produces 4 beats/sec. The first fork is loaded with wax. It again produces 4 beats/sec. When sounded together with the fork of 256 Hz frequency, then the frequency of first tuning fork is
Answer : Option D
Explaination / Solution:
No Explaination.
Q9. Which of the following statements not true?
Answer : Option D
Explaination / Solution:
The net acceleration of a particle in circular motion is along the radius of the circle towards the centre Only in case of uniform circular motion.
Q10. The edge of an aluminum cube is 10 cm long. One face of the cube is firmly fixed to a vertical wall. A mass of 100 kg is then attached to the opposite face of the cube. The shear modulus of aluminum is 25 GPa. What is the vertical deflection of this face?
Answer : Option C
Explaination / Solution:
No Explaination.
