Physics - Online Test
Q1. A circular steel wire 2.00 m long must stretch no more than 0.25 cm when a tensile force of 400 N is applied to each end of the wire. What minimum diameter is required for the wire?
Answer : Option B
Explaination / Solution:
No Explaination.
Q2. An electric heater supplies heat to a system at a rate of 100W. If the system performs work at the rate of 75 joules per second, at what rate is the internal energy increasing?
Answer : Option C
Explaination / Solution:
ΔQ=ΔU+WΔU=100−75=25Watt
Q3. A hydrogen atom initially in the ground level absorbs a photon, which excites it to the n = 4 level. Determine the wavelength and frequency of photon
Answer : Option A
Explaination / Solution:
No Explaination.
Q4.
A bob of mass 0.1 kg hung from the ceiling of a room by a string 2 m long is set into oscillation. The speed of the bob at its mean position is 1 m .What is the trajectory of the bob if the string is cut when the bob is at one of its extreme positions
Answer : Option B
Explaination / Solution:
At the extreme position of the oscillation, the speed of the bob is zero. So the bob is momentarily at rest. if the string is cut, the bob will fall vertically downwards.
Q5. The bob of a pendulum is released from a horizontal position. If the length of the pendulum is 1.5 m, what is the speed with which the bob arrives at the lowermost point, given that it dissipated 5% of its initial energy against air resistance?
Answer : Option D
Explaination / Solution:
95% potential energy is converted in kinetic energy.
applying conservation of mechanical energy between horizontal and lowermost points
Q6. The major contribution of Paul Dirac was in
Answer : Option D
Explaination / Solution:
Paul Dirac was one of the greatest theoretical physicists in history. He completely reshaped quantum mechanics with the astounding Dirac Equation.
The Dirac Equation explained the behavior of electrons and foretold the existence of antimatter. Dirac was also able to infer the existence of vacuum polarization, revealing that what we once believed was empty space is actually awash with short-lived particle-antiparticle pairs.
Q7. In series combination of capacitors, potential drops across the individual capacitors are equal to
Answer : Option A
Explaination / Solution:
When capacitors are connected in series, they have equal charge but the potential difference across them is given by .Therefore
Q8. If a gymnast sitting on a rotating stool with his arms outstretched, suddenly lowers his hands
Answer : Option C
Explaination / Solution:
When gymnast lowers his hand the distance of mass from rotational axis decrease. Hence his moment of inertia decreases and angular velocity increase to conserve angular momentum.
Q9. The surface tension of soap solution is 25 x . The excess pressure inside a soap bubble of diameter 1 cm is
Answer : Option C
Explaination / Solution:
No Explaination.
Q10.
Nine particles have speeds of 5.00, 8.00, 12.0, 12.0, 12.0, 14.0, 14.0, 17.0, and 20.0 m/s. What is the rms speed?
Answer : Option C
Explaination / Solution:
no. of molecule per unit volume
mean free path
