CBSE Class XI Physics Prep
Full explanation, worked examples & memory tricks in the app
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Full explanation, worked examples & memory tricks in the app
Every question in the paper gets a full exam-length answer in the app — organised by marks, the way a topper writes it.
(a) State and prove the law of conservation of mechanical energy for a freely falling body. (b) A body of 2 kg drops from 10 m. Find KE and PE at a height of 4 m. (g = 10 m/s²)
Total energy conserved; KE = 80 J, PE = 40 J.
The full exam-length answer is in the app.
(a) Derive the relation v = ω × r. (b) A flywheel rotating at 1200 rpm decelerates uniformly at 2 rad/s². Find the number of rotations before it stops.
v = ωr; Rotations = 120.
The full exam-length answer is in the app.
(a) Distinguish between conservative and non-conservative forces with examples. (b) Show that work done by a conservative force around a closed loop is zero. (c) Find PE stored in a spring (k=800 N/m) compressed by 5 cm.
Conservative forces: path-independent; W = 0; PE = 10 J.
The full exam-length answer is in the app.
(a) Derive expressions for Time of flight, Max height, and Horizontal range of a horizontal projectile. (b) An aircraft flying horizontally at 490 m high with 180 km/h drops a package. Find the horizontal distance where it lands.
Derive formulas; Distance = 1800 m.
The full exam-length answer is in the app.
Case Study 1: Friction in Daily Life. 1. Why is it easier to pull a lawn roller than to push it? (2 Marks) 2. A mass of 10 kg is on a rough surface (μs=0.5). A force of 40 N is applied. Find the frictional force. (2 Marks)
Pulling reduces normal force, friction is less; Frictional force = 50 N.
The full exam-length answer is in the app.
Case Study 2: Elastic Collisions. 1. Derive the final velocities v1 and v2 after head-on elastic collision with a stationary mass. (2 Marks) 2. If a heavy mass hits a light stationary body, what are the final velocities? (2 Marks)
v1 = (m1 - m2)/(m1 + m2)u; v2 = (2m1)/(m1 + m2)u.
The full exam-length answer is in the app.
(a) Explain the resolution of vectors in a 2D Cartesian plane. (b) Find the angle between vectors A = 2i + 2j - k and B = 6i - 3j + 2k using dot product.
Resolution uses components; Angle = 60°.
The full exam-length answer is in the app.
If a known standard length of 3.52 cm is measured by two instruments as 3.4 cm and 3.512 cm, identify which measurement is more precise and which is more accurate.
3.512 cm is more accurate; 3.512 cm is more precise.
The full exam-length answer is in the app.
Sketch the position-time (x-t) graph for an object moving with (i) positive uniform velocity, and (ii) negative acceleration.
Graph shows a straight line for uniform velocity and a downward curve for negative acceleration.
The full exam-length answer is in the app.
Two masses 5 kg and 10 kg are connected at the two ends of a light inextensible string passing over a frictionless pulley. Find the acceleration of the system when released. (g = 10 m/s2)
Acceleration = 3.33 m/s².
The full exam-length answer is in the app.
State the work-energy theorem for a variable force. Write its mathematical expression in integral form.
Work done = ∫ F dx.
The full exam-length answer is in the app.
Find the torque of a force F = -3i + j + 5k acting at the point r = 7i + 3j + k about the origin.
Torque = (−3i + j + 5k) × (7i + 3j + k).
The full exam-length answer is in the app.
Check the correctness of the relation n = (1/2L) * √(T/m) using dimensional analysis, where n is frequency, L is length, T is tension, and m is mass per unit length.
Dimensions match, relation is correct.
The full exam-length answer is in the app.
Derive the equations of motion v = u + at and s = ut + (1/2)at² using calculus methods.
Use calculus to integrate acceleration to derive equations.
The full exam-length answer is in the app.
Prove that the path followed by a projectile projected at an angle q with the horizontal is parabolic.
Use parametric equations of motion to show parabolic path.
The full exam-length answer is in the app.
Derive an expression for the optimum safe speed of a vehicle on a banked circular smooth track of radius r and angle θ.
Optimum speed = √(rg tan θ).
The full exam-length answer is in the app.
A pump fills a tank of 30 m³ in 15 minutes. The tank is 40 m high. If efficiency is 30%, find electric power consumed. (g=10 m/s²)
Power = 300 W.
The full exam-length answer is in the app.
State and prove the law of conservation of linear momentum using Newton's third law of motion.
Momentum before = Momentum after; proven using collisions.
The full exam-length answer is in the app.
Define radius of gyration. Derive the expression for the moment of inertia of a thin uniform circular ring of mass M and radius R about a tangent perpendicular to its plane.
Radius of gyration k = √(I/M); I = MR².
The full exam-length answer is in the app.
The dimensional formula for absolute permittivity (e0) is:
[M-1L-3T4A2]
The full exam-length answer is in the app.
A student measures the period of oscillation of a simple pendulum. In successive measurements, the readings are 2.63s, 2.56s, 2.42s, 2.71s, and 2.80s. The percentage error in the measurement is closest to:
4%
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A particle moves along a straight line such that its displacement x at time t is given by x = t3 - 6t2 + 3t + 4. The velocity of the particle when its acceleration becomes zero is:
0 m/s
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A bullet fired at an angle of 30° with the horizontal hits the ground 3 km away. By adjusting its angle of projection, keeping the velocity same, the maximum horizontal range achievable is:
6 km
The full exam-length answer is in the app.
If the resultant of two vectors A and B is perpendicular to A and its magnitude is equal to half of the magnitude of B, then the angle between A and B is:
120°
The full exam-length answer is in the app.
A block of mass 2 kg rests on a rough horizontal plane whose coefficient of static friction is 0.4. If a horizontal force of 2.5 N is applied to the block, the frictional force acting on the block will be: (Take g = 10 m/s2)
2.5 N
The full exam-length answer is in the app.
A monkey of mass 40 kg climbs on a rope which can stand a maximum tension of 600 N. In which of the following cases will the rope break? (Take g = 10 m/s2)
climbs up with an acceleration of 6 m/s2
The full exam-length answer is in the app.
The potential energy function for a particle executing linear simple harmonic motion is given by V(x) = kx2/2. If the total energy of the particle is E, then its speed at maximum displacement (x = xmax) is:
Zero
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A body of mass 0.5 kg travels in a straight line with velocity v = ax3/2 where a = 5 m-1/2s-1. The work done by the net force during its displacement from x = 0 to x = 2 m is:
25 J
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A solid cylinder of mass 2 kg and radius 0.2 m is rotating about its central axis at 40 rad/s. The rotational kinetic energy of the cylinder is:
32 J
The full exam-length answer is in the app.
The position vector of the centre of mass of a system of two particles of masses 1 kg and 2 kg located at positions (1,2,1) and (-1,3,-1) respectively is:
(-1/3, 8/3, -1/3)
The full exam-length answer is in the app.
When a net external torque acting on a system becomes zero, which of the following quantities remains strictly conserved?
Angular Momentum
The full exam-length answer is in the app.
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