Physics Mock Test 7 Practice

1. The relative error in the product of two quantities a and b with relative errors δa/a and δb/b is:

• A. δa/a − δb/b
• B. δa/a × δb/b
• C. δa/a + δb/b (Correct)
• D. (δa + δb)/(a × b)

Explanation: For a product P = ab: δP/P = δa/a + δb/b . Relative errors add for products and quotients.

2. The scalar product of a vector with itself, A·A, equals:

• A. 0
• B. A² (square of magnitude) (Correct)
• C. 1
• D. 2A

Explanation: A·A = |A||A|cos0° = A². The dot product of a vector with itself equals the square of its magnitude .

3. A body thrown vertically up passes a point P at height h with velocity v. The maximum height reached above P is:

• A. v/2g
• B. v²/2g (Correct)
• C. v²/g
• D. 2v²/g

Explanation: At P, velocity = v (upward). Extra height above P: using v² = 2gH → H = v²/2g .

4. A bullet fired horizontally at 200 m/s drops 0.1 m in time t. The value of t is (g = 10 m/s²):

• A. 0.1 s
• B. 0.14 s (Correct)
• C. 0.2 s
• D. 0.02 s

Explanation: 0.1 = ½gt² → t² = 0.02 → t = 0.14 s .

5. A feather and a stone dropped simultaneously in vacuum reach the ground:

• A. Stone first
• B. Feather first
• C. Simultaneously (Correct)
• D. Depends on masses

Explanation: In vacuum, all objects fall with same acceleration g. Both reach ground simultaneously .

6. Elastic collision of equal masses (one at rest). After collision:

• A. Both at half speed
• B. First stops, second moves with initial speed (Correct)
• C. Both at right angles
• D. First bounces back

Explanation: Equal-mass elastic: first stops, second takes initial speed .

7. Principle of moments: for equilibrium, sum of clockwise moments equals:

• A. Zero
• B. Sum of anticlockwise moments (Correct)
• C. Net force
• D. Gravitational force

Explanation: Principle of moments: Σclockwise moments = Σanticlockwise moments .

8. Orbital speed of Earth (mass M_sun, distance r):

• A. √(GM_sun r)
• B. GM_sun/r
• C. √(GM_sun/r) (Correct)
• D. 2πr/T

Explanation: v_orbital = √(GM_sun/r). Both expressions √(GM/r) and 2πr/T are correct. Primary formula: √(GM_sun/r) .

9. For a spring (k=200 N/m) stretched by 0.1 m. Elastic PE:

• A. 1 J (Correct)
• B. 20 J
• C. 0.1 J
• D. 2 J

Explanation: PE = ½kx² = ½×200×0.01 = 1 J .

10. In a venturimeter, at the throat (narrowest part):

• A. Pressure is maximum
• B. Velocity is minimum
• C. Pressure is minimum, velocity is maximum (Correct)
• D. Flow stops

Explanation: At throat: smallest area → maximum velocity (continuity) → minimum pressure (Bernoulli). P min, v max .

11. A spring of constant 140 N/m is compressed by 0.1 m. Energy stored is:

• A. 0.7 J (Correct)
• B. 1.4 J
• C. 0.35 J
• D. 14 J

Explanation: Spring energy = (1/2)kx^2 = 0.5 x 140 x 0.01 = 0.7 J.

12. Electric field E has dimensions:

• A. [MLT⁻³A⁻¹] (Correct)
• B. [ML²T⁻³A⁻¹]
• C. [MLT⁻²A⁻¹]
• D. [ML⁻¹T⁻³A⁻¹]

Explanation: E = F/q. [F] = [MLT⁻²], [q] = [AT]. E = [MLT⁻²]/[AT] = [MLT⁻³A⁻¹] .

13. The process of splitting a vector into its rectangular components is called:

• A. Vector addition
• B. Resolution of vectors (Correct)
• C. Scalar multiplication
• D. Vector subtraction

Explanation: Resolution of vectors is the process of finding components of a vector along two perpendicular directions.

14. Two cars start from same point. Car A at 40 km/h, car B at 60 km/h in same direction. After 2 hours separation is:

• A. 20 km
• B. 40 km (Correct)
• C. 100 km
• D. 50 km

Explanation: A covers 80 km, B covers 120 km. Separation = 120 − 80 = 40 km .

15. The angular displacement in 5 seconds of a wheel starting from rest and accelerating at 2 rad/s² is:

• A. 10 rad
• B. 25 rad (Correct)
• C. 50 rad
• D. 100 rad

Explanation: θ = ω₀t + ½αt² = 0 + ½(2)(25) = 25 rad .

16. A 60 kg person in a lift moving down at constant velocity reads on a weighing machine:

• A. More than 600 N
• B. Less than 600 N
• C. 600 N (Correct)
• D. 0 N

Explanation: At constant velocity, acceleration = 0. Apparent weight = mg = 60×10 = 600 N .

17. Coefficient of restitution e for perfectly elastic collision:

• A. 0
• B. 0.5
• C. 1 (Correct)
• D. ∞

Explanation: For perfectly elastic collision, e = 1 .

18. A disc rolls without slipping on level ground. Ratio of KE_rotation to total KE:

• A. 1/2
• B. 1/3 (Correct)
• C. 2/3
• D. 1/4

Explanation: KE_rot = ¼Mv². KE_total = ¾Mv². Ratio = (1/4)/(3/4) = 1/3 .

19. Polar satellites orbit at height ~800 km and have period approximately:

• A. 24 hours
• B. 12 hours
• C. ~100 minutes (Correct)
• D. ~60 minutes

Explanation: Polar satellites (low Earth orbit ~800 km) have period of approximately ~100 minutes .

20. Expansion joints in bridges/railways are provided to:

• A. Increase strength
• B. Allow thermal expansion to avoid thermal stress (Correct)
• C. Reduce weight
• D. Improve aesthetics

Explanation: Expansion joints allow free thermal expansion, preventing dangerous thermal stress buildup.

21. Magnus effect (spinning ball curves) is due to:

• A. Gravity alone
• B. Bernoulli's principle (pressure difference due to spin) (Correct)
• C. Air resistance only
• D. Newton's 1st law

Explanation: Spinning ball: faster air on one side → lower pressure → net force (curve). Bernoulli's principle .

22. A body moves in a circle of radius 3 m with speed 5 m/s. Centripetal acceleration is:

• A. 10.333333333333334 m/s^2
• B. 6.333333333333334 m/s^2
• C. 15 m/s^2
• D. 8.333333333333334 m/s^2 (Correct)

Explanation: Centripetal acceleration = v^2/r = 25/3 = 8.333333333333334 m/s^2.

23. The acceleration due to gravity g is measured by g = 4π²l/T². The value of l = 1.00 m with 1% error, T = 2.00 s with 2% error. The percentage error in g is:

• A. 3%
• B. 5% (Correct)
• C. 7%
• D. 9%

Explanation: % error in g = % error in l + 2 × % error in T = 1% + 2×2% = 1% + 4% = 5% .

24. If position vector r = 3t²î + 2tĵ, then velocity at t = 1 s is:

• A. 3î + 2ĵ
• B. 6î + 2ĵ (Correct)
• C. 6î + ĵ
• D. 3î + ĵ

Explanation: v = dr/dt = 6tî + 2ĵ. At t = 1: v = 6î + 2ĵ m/s.

25. A stone is dropped into a well. The sound of splash is heard after 4 seconds. If speed of sound = 340 m/s and g = 10 m/s², the depth of the well is approximately:

• A. 75 m (Correct)
• B. 300 m
• C. 80 m
• D. 150 m

Explanation: d ≈ 75 m: t₁ = √(2×75/10) = √15 ≈ 3.87 s, t₂ = 75/340 ≈ 0.22 s. Total ≈ 4.09 s ≈ 4 s. Answer: 75 m .

26. A monkey drops from a tree and a hunter fires a bullet aimed at the monkey at the same instant. The bullet:

• A. Always misses
• B. Hits only at 45° angle
• C. Always hits the monkey (Correct)
• D. Hits only if gun is horizontal

Explanation: Both bullet and monkey fall the same vertical distance under gravity. The bullet always hits the monkey regardless of angle or speed.

27. A 10 kg block on rough surface (μₛ = 0.5, μₖ = 0.4) is pushed by 40 N. Acceleration (g = 10 m/s²):

• A. 0 m/s² (Correct)
• B. 2 m/s²
• C. 1 m/s²
• D. 4 m/s²

Explanation: Max static friction = μₛmg = 50 N > 40 N (applied force). Block does not move. Acceleration = 0 m/s² .

28. Which quantity is ALWAYS conserved in any collision?

• A. Kinetic energy
• B. Momentum (Correct)
• C. Potential energy
• D. Temperature

Explanation: Total momentum is always conserved in any collision.

29. Two discs (I₁, I₂, ω₁, 0) are pressed together. Combined ω:

• A. (I₁ω₁+I₂×0)/(I₁+I₂)
• B. I₁ω₁/(I₁+I₂) (Correct)
• C. ω₁/2
• D. I₁ω₁/I₂

Explanation: Conservation of L: I₁ω₁ = (I₁+I₂)ω. ω = I₁ω₁/(I₁+I₂) .

30. Work done by gravitational force moving mass m from r₁ to r₂ (r₂ > r₁):

• A. GMm(1/r₁−1/r₂) (Correct)
• B. GMm(1/r₂−1/r₁)
• C. −GMm/r₁
• D. GMm×r₁

Explanation: W = −ΔPE = −[−GMm/r₂ − (−GMm/r₁)] = GMm(1/r₁−1/r₂) . (Negative as r increases.)

31. Theoretical range of Poisson's ratio (−1 to 0.5). For liquids ν =:

• A. 0
• B. 0.5 (Correct)
• C. 1
• D. −1

Explanation: Liquids are incompressible → ν = 0.5 .

32. Maximum range of efflux from a tank (height H, hole at height y from bottom):

• A. y = H
• B. y = H/2 (Correct)
• C. y = H/4
• D. y = 0

Explanation: Range R = 2√(y(H−y)). Maximized when y = H/2 → R_max = H. Hole at y = H/2 .

33. Two perpendicular vectors have magnitudes 5 and 6. Their resultant magnitude is approximately:

• A. 1
• B. 30.0
• C. 7.8 (Correct)
• D. 11

Explanation: For perpendicular vectors, R = sqrt(5^2 + 6^2) = 7.8.

34. The physical quantity that has the dimensions [M⁰L⁰T⁰] is:

• A. Displacement
• B. Velocity
• C. Strain (Correct)
• D. Force

Explanation: Strain = change in length/original length = dimensionless = [M⁰L⁰T⁰]. All other options have non-zero dimensions.

35. Three forces in equilibrium must be:

• A. All equal in magnitude
• B. All parallel
• C. Coplanar and concurrent (Correct)
• D. All perpendicular

Explanation: For three forces to be in equilibrium, they must be coplanar (in the same plane) and concurrent (meeting at a point).

36. The braking distance of a vehicle moving at speed v with deceleration a is:

• A. v/a
• B. v²/2a (Correct)
• C. 2v/a
• D. v²/a

Explanation: v² = u² − 2as. At rest: 0 = v² − 2a·s → s = v²/2a .

37. Which of the following is NOT true for uniform circular motion?

• A. Speed is constant
• B. Magnitude of acceleration is constant
• C. Kinetic energy is constant
• D. Velocity is constant (Correct)

Explanation: In uniform circular motion, speed, |acceleration|, and kinetic energy remain constant. However, velocity changes continuously since direction changes.

38. Action and reaction forces are:

• A. Always in the same direction
• B. Always equal in magnitude (Correct)
• C. Acting on the same body
• D. Unequal in magnitude

Explanation: By Newton's Third Law, action and reaction forces are always equal in magnitude (opposite in direction, different bodies).

39. Pump (efficiency 80%) raises 1000 L water/min to 10 m (g = 10 m/s²). Input power required:

• A. 2083 W (Correct)
• B. 1667 W
• C. 2000 W
• D. 1333 W

Explanation: P_out = 1000×10×10/60 = 1667 W. P_in = 1667/0.8 = 2083 W .

40. A body is in stable equilibrium when:

• A. COM is highest
• B. COM is lowest possible (Correct)
• C. COM is at geometric centre
• D. No forces act

Explanation: Stable equilibrium: COM is at the lowest possible position (minimum PE).

41. Mars is ~1.52 AU from Sun. Its orbital period (Earth's = 1 year, 1 AU = Earth-Sun distance):

• A. ~1.87 years (Correct)
• B. ~3.5 years
• C. ~1.52 years
• D. ~2.3 years

Explanation: T² ∝ r³. T = (1.52)^(3/2) ≈ 1.52^1.5 ≈ 1.87 years .

42. The area under the stress-strain curve up to fracture represents:

• A. Young's modulus
• B. Toughness (Correct)
• C. Hardness
• D. Brittleness

Explanation: Area under entire stress-strain curve = energy absorbed before fracture = toughness .

43. Blood flows faster in capillaries OR arteries? (Capillaries have small radius but far more in number.)

• A. Capillaries
• B. Arteries (Correct)
• C. Same
• D. Veins

Explanation: Total cross-section of capillaries >> arteries. By continuity, v is slower in capillaries , faster in arteries .

44. In a NEET physics drill, a particle starts with speed 11 m/s and acceleration 2 m/s^2 for 3 s. Final speed is:

• A. 33 m/s
• B. 17 m/s (Correct)
• C. 15 m/s
• D. 19 m/s

Explanation: Use v = u + at = 11 + 2 x 3 = 17 m/s.

45. Which instrument is used for measuring very small lengths of the order of 10⁻⁵ m?

• A. Vernier caliper
• B. Metre scale
• C. Screw gauge (Correct)
• D. Optical microscope

Explanation: A screw gauge (micrometer screw gauge) has a least count of 0.01 mm = 10⁻⁵ m, suitable for measuring very small lengths like wire diameter.

46. The derivative of a constant is:

• A. 1
• B. ∞
• C. 0 (Correct)
• D. The constant itself

Explanation: d(c)/dx = 0 for any constant c. The graph of a constant is a horizontal line with zero slope.

47. The standard acceleration due to gravity g is approximately:

• A. 9.8 cm/s²
• B. 9.8 m/s² (Correct)
• C. 98 m/s²
• D. 0.98 m/s²

Explanation: The standard value is g ≈ 9.8 m/s² (approximated as 10 m/s² in problems).

48. If the radius of a circular path is doubled while angular velocity remains same, the centripetal force is:

• A. Same
• B. Doubled (Correct)
• C. Halved
• D. Quadrupled

Explanation: F = mω²r. If r doubles: F = mω²(2r) = 2mω²r. Centripetal force is doubled .

49. Net force on a 5 kg body if velocity v = 3t² − 2t is:

• A. (30t − 10) N (Correct)
• B. (6t − 2) N
• C. (18t − 6) N
• D. (15t² − 5t) N

Explanation: a = dv/dt = 6t − 2. F = ma = 5(6t−2) = 30t − 10 N .

50. 10 g bullet embeds in 1 kg block (at rest). Bullet speed 300 m/s. Block speed after:

• A. 2.97 m/s (Correct)
• B. 3 m/s
• C. 0.3 m/s
• D. 30 m/s

Explanation: 0.01×300 = 1.01×v. v = 3/1.01 ≈ 2.97 m/s .

51. A ball (m=0.1 kg) is attached to a string and moves in horizontal circle (r=0.5 m, v=2 m/s). Angular momentum:

• A. 0.1 kg·m²/s (Correct)
• B. 0.2 kg·m²/s
• C. 0.4 kg·m²/s
• D. 1 kg·m²/s

Explanation: L = mvr = 0.1×2×0.5 = 0.1 kg·m²/s .

52. In elliptical orbit, where is satellite's KE maximum?

• A. Apogee
• B. Perigee (Correct)
• C. Constant throughout
• D. Midpoint

Explanation: At perigee (closest point), speed is maximum → KE is maximum.

53. Two wires (same Y, same stress). Wire B has twice the volume. Ratio of elastic PE (A/B):

• A. 1/2 (Correct)
• B. 2
• C. 1/4
• D. 1

Explanation: u = σ²/2Y (same for both). PE = u×V. PE_A/PE_B = V_A/V_B = 1/2 .

54. Dynamic pressure (½ρv²) represents:

• A. Potential energy per unit volume
• B. Kinetic energy per unit volume (Correct)
• C. Work done per unit area
• D. Pressure due to depth

Explanation: ½ρv² = kinetic energy per unit volume (dynamic pressure).

55. A block of mass 2 kg accelerates at 3 m/s^2. Net force on it is:

• A. 6 N (Correct)
• B. 9 N
• C. 3 N
• D. 12 N

Explanation: By Newton's second law, F = ma = 2 x 3 = 6 N.

56. The dimensions of the universal gas constant R are:

• A. [ML²T⁻²K⁻¹mol⁻¹] (Correct)
• B. [MLT⁻²K⁻¹]
• C. [ML²T⁻²mol⁻¹]
• D. [ML²T⁻¹K⁻¹mol⁻¹]

Explanation: From PV = nRT, R = PV/(nT). [P] = [ML⁻¹T⁻²], [V] = [L³], [n] = [mol], [T] = [K]. R = [ML⁻¹T⁻²·L³/(mol·K)] = [ML²T⁻²K⁻¹mol⁻¹] .

57. Two forces of equal magnitude F make an angle of 120° with each other. The magnitude of their resultant is:

• A. F (Correct)
• B. 2F
• C. F√3
• D. F/√2

Explanation: R = √(F²+F²+2F²cos120°) = √(2F²−F²) = F .

58. A body falling freely from height H has velocity v at height H/4 from ground. Then v is:

• A. √(gH/2)
• B. √(gH)
• C. √(3gH/2) (Correct)
• D. √(3gH/4)

Explanation: Body falls from H to H/4, covering 3H/4. v² = 2g(3H/4) = 3gH/2 → v = √(3gH/2) .

59. A projectile has the same range for angles α and β where α + β = 90°. If H₁ and H₂ are max heights, then H₁ + H₂ equals:

• A. R/2 (Correct)
• B. R/4
• C. R
• D. 2R

Explanation: H₁ = u²sin²α/2g, H₂ = u²cos²α/2g. H₁+H₂ = u²(sin²α+cos²α)/2g = u²/2g. At 45°, R = u²/g. So H₁+H₂ = R/2 (the range at 45°). Answer: R/2 .

60. A 50 g stone tied to a 1 m string whirled in horizontal circle at 2 m/s. Centripetal force is:

• A. 0.1 N
• B. 0.2 N (Correct)
• C. 0.4 N
• D. 1 N

Explanation: F = mv²/r = (0.05)(4)/1 = 0.2 N .