CBSE 11TH PHYSICS - Online Test
Q1. Consider the collision of two cars. Car 1 is at rest and Car 2 is moving at a speed of 2 m /s in the negative x-direction. Both cars each have a mass of 500 kg. The cars collide inelastically and stick together. What is the resulting velocity of the resulting mass of metal?
Answer : Option B
Explaination / Solution:
from conservation of linear momentum initial momentum = final momentum
negative sign indicate that cars moves to the left.
Q2. Fundamental forces in nature are those
Answer : Option A
Explaination / Solution:
The universe has a lot of forces, a lot of pushes and pulls. We're always pushing or pulling something, even if only the ground. But it turns out that in physics, there are really only four fundamental forces from which everything else is derived: the strong force, the weak force, the electromagnetic force, and the gravitational force.
Q3. A fly wheel rotating about a fixed axis has a kinetic energy of 360 joule when its angular speed is 30 radians per second. The moment of inertia of the fly wheel about the axis of rotation is
Answer : Option B
Explaination / Solution:
K=12Iω2K=360Jω=30rad/sI=2Kω2=2×36030×30=0.8Kgm2
Q4. When a soap bubble is charged, it
Answer : Option B
Explaination / Solution:
Charge will be distributed uniformly on the surface of a bubble if the bubble is charged.The bubble will expand because the charged particles uniformly distributed on it cause them to repel each other due to the electrostatic force. This will happen to both positive and negatively charged bubbles because of the charge on it.
Q5. In a 30.0-s interval, 500 hailstones strike a glass window with an area of 0.600 at an angle of 45.0 to the window surface. Each hailstone has a mass of 5.00 g and a speed of 8.00 m/s. If the collisions are elastic, what are the average force and pressure on the window?
Answer : Option B
Explaination / Solution:
Q6.
The electrical resistance in ohms of a certain thermometer varies with temperature according to the approximate law : R =R[1 + (T –T )] The resistance is 101.6 at the triple-point of water 273.16 K, and 165.5 at the normal melting point of lead (600.5 K). What is the temperature when the resistance is 123.4 ?
Answer : Option C
Explaination / Solution:
It is given that:
R = R0 [1 +
R0 and T0 are the initial resistance and temperature respectively
R and T are the final resistance and temperature respectively
is a constant
At the triple point of water, T0 = 273.15 K
Resistance of lead, R0 = 101.6
At normal melting point of lead, T = 600.5 K
Resistance of lead, R = 165.5
Substituting these values in equation (i), we get:
R = Ro [1 + (T – To)]
165.5 = 101.6 [ 1 + (600.5 - 273.15) ]
1.629 = 1 + (327.35)
∴ = 0.629 / 327.35 = 1.92 × 10-3 K-1
For resistance, R1 = 123.4
R1 = R0 [1 + (T – T0)]
where,
T is the temperature when the resistance of lead is 123.4
123.4 = 101.6 [ 1 + 1.92 × 10-3( T - 273.15) ]
Solving for T, we get
T = 384.8 K.
R = R0 [1 +
- (T – T0)] … (i)
R0 and T0 are the initial resistance and temperature respectively
R and T are the final resistance and temperature respectively
is a constant
At the triple point of water, T0 = 273.15 K
Resistance of lead, R0 = 101.6
At normal melting point of lead, T = 600.5 K
Resistance of lead, R = 165.5
Substituting these values in equation (i), we get:
R = Ro [1 + (T – To)]
165.5 = 101.6 [ 1 + (600.5 - 273.15) ]
1.629 = 1 + (327.35)
∴ = 0.629 / 327.35 = 1.92 × 10-3 K-1
For resistance, R1 = 123.4
R1 = R0 [1 + (T – T0)]
where,
T is the temperature when the resistance of lead is 123.4
123.4 = 101.6 [ 1 + 1.92 × 10-3( T - 273.15) ]
Solving for T, we get
T = 384.8 K.
Q7. The number of significant digits in 0.007 is
Answer : Option B
Explaination / Solution:
There are three rules on determining how many significant figures are in a number:
- Non-zero digits are always significant.
- Any zeros between two significant digits are significant.
- A final zero or trailing zeros in the decimal portion ONLY are significant.
So keeping these rules in mind, there are 1 significant digit.
Q8. A mass M is suspended from a spring of negligible mass. The spring is pulled a little and then released so that the mass executes simple harmonic oscillations with a time period T.
Answer : Option D
Explaination / Solution:
No Explaination.
Q9. A stone thrown from the top of a building is given an initial velocity of 20.0 m/s straight upward. Determine the time in seconds at which the stone reaches its maximum height. g =9.8 m /
Answer : Option D
Explaination / Solution:
Initial velocity u = 20.0 m/s
At maximum height it ll stop
So final velocity v = 0 m/s
Acceleration due to gravity g = 9.8 m/s2
Time taken to reach maximum height = t
We know
v = u + at
=>
[g is taken negative because it is in opposite direction of motion.]
Q10. A tuning fork produces 4 beats/sec. with 50 cm and 40 cm of a stretched wire, of a sonometer. The frequency of fork is
Answer : Option B
Explaination / Solution:
No Explaination.
