Join 60,000+ competitive exam aspirants
or with email
Your Cart
Subtotal₹0
Total₹0
Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
Join 60,000+ competitive exam aspirants
A car has a mass of 120 kg. How much work must be done to raise its speed from 72 km/h to 108 km/h?
0 × 10⁴ J
0 × 10⁴ J
0 × 10⁴ J
0 × 10⁴ J
0 × 10⁴ J
The work done to change the speed of an object is equal to the change in its kinetic energy, defined by the Work-Energy Theorem. By calculating the difference between the final kinetic energy and the initial kinetic energy, we determine that the work done is 3.0×104 J.
The work done to change the speed of an object is equal to the change in its kinetic energy, defined by the Work-Energy Theorem. By calculating the difference between the final kinetic energy and the initial kinetic energy, we determine that the work done is 3.0×104 J.
Increasing the speed of a car is like stretching a spring; the more you stretch it (or the faster you make the car go), the more energy you have to 'invest' into the system.
W=ΔKE=21m(vf2−vi2) — Work-Energy Theorem relating work to change in kinetic energy
vm/s=vkm/h×185 — Conversion factor for velocity units
The Work-Energy Theorem states that W=ΔK=21m(vf2−vi2). First, convert velocities from km/h to m/s by multiplying by 185: vi=72×185=20 m/s and vf=108×185=30 m/s. Substituting these into the formula: W=21×120×(302−202)=60×(900−400)=60×500=30,000 J, or 3.0×104 J.
The Work-Energy Theorem is independent of the time taken to change the speed.
Kinetic energy increases with the square of the velocity.
Always convert speed units to SI units (m/s) before calculation.
Provides a direct method to find work without needing force or displacement values.
Assumes a frictionless environment where all work contributes to changing kinetic energy.
Determining fuel consumption requirements for vehicle acceleration.
Braking distance calculations in automotive engineering.
Initial velocity vi=20 m/s, Final velocity vf=30 m/s.
Option B, C, and D are results of common calculation errors, such as neglecting the squared terms or incorrect unit conversion.
A is correct — The work done is equivalent to the increase in the kinetic energy of the 120 kg car as it accelerates from 20 m/s to 30 m/s.
Always verify unit consistency first; forgetting to convert km/h to m/s is the most common reason for getting this specific physics problem wrong.
Get instant step-by-step AI explanations, full shift Previous Year Papers (SSC GD, RRB, SSC JE), and regional rank analysis on the official Examoogle App.
Free Download • 100K+ Aspirants