Physics - Online Test
Q1. for a signal to be reproduced without distortion
Answer : Option A
Explaination / Solution:
No Explaination.
Q2. A cricketer can throw a ball to a maximum horizontal distance of 100 m. How much high above the ground can the cricketer throw the same ball?
Answer : Option D
Explaination / Solution:
Maximum horizontal distance, R = 100 m
The cricketer will only be able to throw the ball to the maximum horizontal distance when the angle of projection is 45°, i.e., θ = 45°.
The horizontal range for a projection velocity v, is given by the relation:
R =( u2 Sin 2θ / g)
100 =
=> = 100 ….(i)
The ball will achieve the maximum height when it is thrown vertically upward. For such motion, the final velocity v is zero at the maximum height H.
Acceleration, a = –g
Using the third equation of motion:
v2 – u2 = -2gH
The cricketer will only be able to throw the ball to the maximum horizontal distance when the angle of projection is 45°, i.e., θ = 45°.
The horizontal range for a projection velocity v, is given by the relation:
R =( u2 Sin 2θ / g)
100 =
=> = 100 ….(i)
The ball will achieve the maximum height when it is thrown vertically upward. For such motion, the final velocity v is zero at the maximum height H.
Acceleration, a = –g
Using the third equation of motion:
v2 – u2 = -2gH
Q3. A tennis ball which has been covered with charges is suspended by a thread so that it hangs between two metal plates. One plate is earthed, while other is attracted to a high voltage generator. The ball
Answer : Option C
Explaination / Solution:
The plate which connected to high voltage generator induces negative charge on ball which causes attraction. When the ball strikes the positive plate, charge distribution again takes place that is the bass becomes positive and repulsion takes place. When it strikes the plate which connected to earth than its charge goes to earth and again it will be attracted towards positive plate. Hence the ball swings backward and forward hitting each plate in turn.
Q4. A steel rod 2.0 m long has a cross-sectional area of 0.30 . It is hung by one end from a support, and a 550-kg milling machine is hung from its other end. Determine the elongation. Take Young's modulus of steel as 20 Pa
Answer : Option C
Explaination / Solution:
No Explaination.
Q5. Two cylinders A and B of equal capacity are connected to each other via a stopcock. A contains a gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stopcock is suddenly opened. What is the change in internal energy of the gas?
Answer : Option B
Explaination / Solution:
Internal energy depends on temperature and temperature remains constant because system is thermally insulated. so that change in internal energy will be zero.
Q6. In which of the models An atom has a nearly continuous mass distribution?
Answer : Option B
Explaination / Solution:
No Explaination.
Q7. A rocket with a lift-off mass 20,000 kg is blasted upwards with an initial acceleration of 5.0 m s-2. Calculate the initial thrust (force) of the blast.
Answer : Option A
Explaination / Solution:
Initial thrust = upthrust required to impart acceleration + uthrust to overcome gravity
=
Q8. A weight of 20kg falls from a height of 10 m. The work done by the gravitational force is (Take g = 10 m )
Answer : Option C
Explaination / Solution:
W=Fscosθ=mghcos0∘W=20×10×10×1=2000J
Q9. The major contribution of C.V. Raman was
Answer : Option A
Explaination / Solution:
The Indian physicist C.V. Raman helped the growth of science in his country. He received the Nobel Prize for Physics in 1930 for the discovery that when light passes through a transparent material, some of the light changes in wavelength. This phenomenon is now called Raman scattering.
Q10. A variable capacitor and an electroscope are connected in parallel to a battery. The reading of the electroscope would be decreased by
Answer : Option C
Explaination / Solution:
An electroscope is a device which measures the potential difference. If it is connected in parallel to the capacitor, the potential across it will be equal to the potential across the capacitor, which is equal to the potential across the battery. On decreasing the battery potential, the potential difference across the electroscope reduces and hence the reading reduces. While the capacitor is connected to the battery, Placing a dielectric between the plates, or decreasing the distance between the plates or increasing the area of the plates will not change the potential difference across it; since it will always remain equal to the potential difference maintained by the battery. In the cases B, C and D, The capacitance of the capacitor , however increases ; but this increase happens due to increase in the charge stored in the capacitor while the potential remains constant.
