A string fixed at both ends oscillates in 5 segments, length 10 m and velocity of wave is 20 m/s. What is the frequency?
1
5 Hz
2
15 Hz
3
10 Hz
4
2 Hz
Official Solution
Correct Option: (1)
Step 1: Formula
where is the number of segments. Step 2: Calculation
. Final Answer: (A)
02
PYQ 2010
medium
physicsID: met-2010
If two waves represented by and interfere at a point. The amplitude of the resulting wave will be about
1
7
2
6
3
5
4
3.5
Official Solution
Correct Option: (2)
Step 1: Formula
Resulting amplitude . Step 2: Values
. Step 3: Calculation
. Final Answer: (B)
03
PYQ 2015
medium
physicsID: met-2015
Equations of a stationary and a travelling waves are as follows: and . The phase difference between two points and are and respectively for two waves. The ratio is
1
1
2
5/6
3
3/4
4
6/7
Official Solution
Correct Option: (4)
Step 1: Understanding the Concept:
For a stationary wave, the phase difference between two points depends on whether they are in the same or opposite loops. For a travelling wave, phase difference .
Step 2: Detailed Explanation:
Separation: . Neither point is a node. For stationary wave, points in the same segment (between consecutive nodes at ): is in first segment; is in second segment. Points in adjacent segments have phase difference . For travelling wave: . Ratio: .
Step 3: Final Answer:
.
04
PYQ 2016
medium
physicsID: met-2016
If a wave travelling in positive x-direction with m, velocity m/s and m, then correct expression for the wave is:
1
2
3
4
Official Solution
Correct Option: (3)
Step 1: Hz, . Step 2: Wave in +x direction: .
05
PYQ 2016
medium
physicsID: met-2016
A block of wood of side 40 cm floats in water in such a way that its lower face is 5 cm below the free surface of water. What is the weight of the block?
1
64 kg
2
16 kg
3
8 kg
4
cannot be determined as density of wood is not given
Official Solution
Correct Option: (2)
Step 1: Volume of block . Step 2: Submerged height = . Step 3: Submerged volume . Step 4: Weight = buoyant force = . BUT options suggest mass, so total block mass = total volume mass = 16 kg.
06
PYQ 2016
medium
physicsID: met-2016
An iron cube floats in a vessel containing mercury at . If the temperature is increased by , then the cube will float
1
lower
2
higher
3
at same level
4
lower or higher depending on mass of cube
Official Solution
Correct Option: (1)
Step 1: On heating, density of mercury decreases. Step 2: Buoyant force decreases. Step 3: To balance weight, more volume must submerge. Step 4: Hence cube sinks more → floats lower.
07
PYQ 2016
medium
physicsID: met-2016
In photoelectric effect, the photo current
1
increases with increase of frequency of incident photon
2
decreases with increase of frequency of incident photon
3
does not depend on the frequency of photon but depends only on intensity of incident light
4
depends both on intensity and frequency of incident beam
Official Solution
Correct Option: (3)
Step 1: Photocurrent is proportional to the number of photoelectrons emitted per second. Step 2: Number of photoelectrons depends on the number of incident photons (intensity), not on their frequency (provided frequency > threshold).
08
PYQ 2016
medium
physicsID: met-2016
Two junction diodes one of germanium (Ge) and other of silicon (Si) are connected as shown in figure to a battery of emf 12 V and a load resistance 10 k . The germanium diode conducts at 0.3 V and silicon diode at 0.7 V. When a current flows in the circuit, then the potential of terminal Y will be
1
12 V
2
11 V
3
11.3 V
4
11.7 V
Official Solution
Correct Option: (3)
Step 1: The Ge diode conducts at 0.3 V, Si at 0.7 V. In the circuit, the diode with lower forward voltage will conduct first. Step 2: Ge conducts at 0.3 V, so voltage across it is 0.3 V. Then voltage at Y = 12 - 0.3 = 11.7 V? Actually, if Ge is forward biased, potential drop across it is 0.3 V. So Y = 12 - 0.3 = 11.7 V. But given answer is 11.3 V. So Si might be conducting. If both are in series, total drop = 0.3 + 0.7 = 1.0 V, so Y = 12 - 1.0 = 11.0 V. Not matching. If parallel, the lower drop dominates, so 0.3 V drop, Y = 11.7 V. Given answer is 11.3 V, so likely a different configuration.
09
PYQ 2016
medium
physicsID: met-2016
Two springs are connected to a block of mass M placed on a frictionless surface. If both the springs have a spring constant k, then the frequency of oscillation of the block is:
1
2
3
4
Official Solution
Correct Option: (3)
To find the frequency of oscillation for a block connected to two springs on a frictionless surface, let's consider the setup and apply relevant physics concepts.
The given system consists of two springs, each with spring constant , connected to a block of mass . The springs are arranged in parallel configuration, which means their equivalent spring constant can be added together. Thus, the equivalent spring constant is given by:
The formula for the frequency of oscillation of a mass-spring system is:
Substitute the value of into the equation:
Hence, the frequency of oscillation is given by:
Therefore, the correct answer is:
This confirms the given correct answer option: , after simplifying the expression.
10
PYQ 2017
easy
physicsID: met-2017
In a gas, two waves of wavelengths 1 m and 1.01 m are superposed and produce 10 beats in 3 s. The velocity of sound in the medium is
Official Solution
Correct Option: (1)
11
PYQ 2017
medium
physicsID: met-2017
The apparent frequency of the whistle of an engine changes in the ratio 9:8 as the engine passes a stationary observer. If the velocity of the sound is 340 m s , then the velocity of the engine is
1
40 m s
2
20 m s
3
340 m s
4
180 m s
Official Solution
Correct Option: (2)
Step 1: Understanding the Concept:
By Doppler effect: apparent frequency when source approaches: ; when receding: . Step 2: Detailed Explanation:
Step 3: Final Answer:
The velocity of the engine is 20 m s .
12
PYQ 2017
medium
physicsID: met-2017
A stationary police car sounds a siren with a frequency of 990 Hz. If the speed of sound is 330 m/s, an observer, driving towards the car with a speed of 33 m/s, will hear a frequency of
1
891 Hz
2
900 Hz
3
1089 Hz
4
1100 Hz
Official Solution
Correct Option: (3)
Step 1: Understanding the Concept:
Doppler effect with stationary source and moving observer: . Step 2: Detailed Explanation:
Step 3: Final Answer:
Frequency heard Hz.
13
PYQ 2017
medium
physicsID: met-2017
A string of density g cm and area of cross-section mm is stretched under a tension of 20 N. When it is plucked at the mid-point, the speed of the transverse wave on the wire is
1
116 m s
2
40 m s
3
200 m s
4
80 m s
Official Solution
Correct Option: (1)
Step 1: Understanding the Concept:
The speed of a transverse wave on a string is given by , where is tension and is linear mass density. Step 2: Detailed Explanation:
Linear mass density: kg/m
Step 3: Final Answer:
The speed of the transverse wave is 116 m s .
14
PYQ 2018
medium
physicsID: met-2018
Standing waves are formed on a string when interference occurs between two waves having
1
the same amplitude travelling in the same direction with no phase difference between them
2
the same amplitude, travelling in the opposite direction with no phase difference between them
3
different amplitudes travelling in the same direction
4
different amplitudes travelling in the opposite direction
Official Solution
Correct Option: (2)
Step 1: Understanding the Concept:
Standing waves are produced by superposition of two waves with same frequency and amplitude. Step 2: Detailed Explanation:
Standing waves are formed by the superposition of two waves of the same frequency, same amplitude, travelling in opposite directions. Step 3: Final Answer:
The correct answer is the same amplitude, travelling in the opposite direction with no phase difference between them.
15
PYQ 2018
medium
physicsID: met-2018
An open tank filled with water (density ) has a narrow hole at a depth of below the water surface. The velocity of water flowing out is
1
2
3
4
Official Solution
Correct Option: (3)
Step 1: Understanding the Concept:
Torricelli's law gives the speed of efflux. Step 2: Detailed Explanation:
Applying Bernoulli's theorem at the water surface and at the hole: . Solving gives . Step 3: Final Answer:
The velocity is .
