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Q.33 Physics · Section A ⭐ 360° Option Elimination Active
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NEET 2024 Physics Question 33 Solution

Topic: Work, Energy and Power · Official NTA Booklet Code T1
NEET 2024 Physics Question 33: Instantaneous Power Delivered by a Constant Force

Question

At any instant of time t, the displacement of any particle is given by 2t − 1 (SI unit) under the influence of force of 5 N. The value of instantaneous power is (in SI unit):

✓
Verified Against NTA Final Answer Key
Option (3) : 10
📚 Work, Energy and Power Easy
📋 Given Parameters & Problem Setup
Displacement function x(t) = 2t - 1 (in SI units)
Applied force F = 5 N
⚡

The 30-Second Exam Hall Shortcut: ⚡ Velocity Derivative Shortcut

⏱️ Save ~30 seconds

v = dx/dt = d(2t - 1)/dt = 2 m/s -> Instantaneous Power P = F × v = 5 × 2 = 10 W!

1 Differentiate displacement to find velocity: v = dx/dt = 2 m/s (constant velocity).
2 Instantaneous power is given by scalar product P = F · v.
3 Substitute F = 5 N and v = 2 m/s: P = 5 × 2 = 10 W (SI units).
4 Option (3) in 3 seconds!
🛡️
Why You Can 100% Trust This Shortcut: Definition of Instantaneous Power (P = F · v = F · dx/dt).
📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Velocity Determination from Displacement

The velocity v of the particle is the first time derivative of its position function x(t) = 2t - 1:

v(t)=dxdt=ddt(2t−1)=2 m/sv(t) = \frac{dx}{dt} = \frac{d}{dt}(2t - 1) = 2\,\text{m/s}
Step 2

Formula for Instantaneous Power

Instantaneous power P delivered by a force F to a particle moving with velocity v in the same direction is:

P=F⃗⋅v⃗=F⋅vP = \vec{F} \cdot \vec{v} = F \cdot v
Step 3

Calculation of Power

Substituting F = 5 N and v = 2 m/s:

P=(5 N)(2 m/s)=10 W(SI units)P = (5\,\text{N})(2\,\text{m/s}) = 10\,\text{W} \quad (\text{SI units})
⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan
1 (1)
✗ Incorrect
Verdict & Scientific Reason:

Adds force and velocity (5 + 2 = 7) instead of multiplying.

⚠️
Student Fallacy (Why candidates pick this trap): Failing to apply scalar product.
2 (2)
✗ Incorrect
Verdict & Scientific Reason:

Arbitrary calculation error.

⚠️
Student Fallacy (Why candidates pick this trap): Evaluating at specific time t = 1.
3 (3)
✓ 100% Correct
Verdict & Scientific Reason:

Exact product: P = F × v = 5 × 2 = 10 SI units.

💡
Why this is airtight: None.
4 (4)
✗ Incorrect
Verdict & Scientific Reason:

Assumes velocity is 1 m/s.

⚠️
Student Fallacy (Why candidates pick this trap): Ignoring the coefficient 2 in displacement.
⚠️

NTA Trap Alert: Plugging in Time t

Students search for a value of t to plug into 2t - 1, getting confused because velocity is constant.

🛡️ How to avoid the -1 mark: Notice that dx/dt = 2 is independent of time t! Power is constant at 10 W for all t.
📖

Core NEET Syllabus Standard

Physics Core Mechanics · Work, Energy and Power Standard Benchmark
Core Scientific Principle Tested:

"Instantaneous power is the rate of doing work, given by the dot product of force and instantaneous velocity: P = F · v."

Syllabus Focus: Work and Power
✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗
Differentiate position to get 2; Multiply by 5 and 10 shines through!

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