back to directory
NEET PHYSICSWORK, ENERGY AND POWERMedium

Question

A block of mass 10 kg10 \text{ kg}, moving in the xx-direction with a constant speed of 10 m/s10 \text{ m/s}, is subjected to a retarding force F=0.1x J/mF = 0.1x \text{ J/m} during its travel from x=20 mx = 20 \text{ m} to 30 m30 \text{ m}. Its final kinetic energy will be:

A

475 J

B

450 J

C

275 J

D

250 J

Step-by-Step Solution

  1. Calculate Initial Kinetic Energy (KiK_i): Given mass m=10 kgm = 10 \text{ kg} and initial speed v=10 m/sv = 10 \text{ m/s}. Ki=12mv2=12(10)(10)2=500 JK_i = \frac{1}{2}mv^2 = \frac{1}{2}(10)(10)^2 = 500 \text{ J} (Refer to NCERT Class 11, Section 5.4, Eq. 5.5).
  2. Calculate Work Done by Variable Force (WW): The force is variable (F=0.1xF = 0.1x) and retarding (opposes motion). The work done by a variable force is calculated by integration. W=xixfF(x)dxW = \int_{x_i}^{x_f} F(x) dx Since it is a retarding force, we take it as negative or subtract the work magnitude from initial energy. W=2030(0.1x)dx=0.1[x22]2030W = \int_{20}^{30} (-0.1x) dx = -0.1 \left[ \frac{x^2}{2} \right]_{20}^{30} W=0.05(302202)=0.05(900400)W = -0.05 (30^2 - 20^2) = -0.05 (900 - 400) W=0.05(500)=25 JW = -0.05 (500) = -25 \text{ J} (Refer to NCERT Class 11, Section 5.5, Eq. 5.7 regarding work done by variable force).
  3. Apply Work-Energy Theorem: The change in kinetic energy is equal to the work done. KfKi=WK_f - K_i = W Kf=Ki+W=500+(25)=475 JK_f = K_i + W = 500 + (-25) = 475 \text{ J} (Refer to NCERT Class 11, Section 5.6 for the Work-Energy Theorem).

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from WORK, ENERGY AND POWER. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSWORK, ENERGY AND POWERmovingxdirectionconstantsubjectedretarding

More WORK, ENERGY AND POWER Questions

View all

A $100 \text{ g}$ iron ball having velocity $10 \text{ m/s}$ collides with a wall at an angle $30^\circ$ and rebounds with the same angle. If the period of contact between the ball and wall is $0.1 \text{ second}$, then the force experienced by the wall is:

A.$10 \text{ N}$
B.$100 \text{ N}$
C.$1.0 \text{ N}$
D.$0.1 \text{ N}$
MediumSolve

An object of mass $500 \text{ g}$ initially at rest is acted upon by a variable force whose $x$-component varies with $x$ in the manner shown. The velocities of the object at the points $x=8 \text{ m}$ and $x=12 \text{ m}$ would have the respective values of nearly:

A.18 m/s and 22.4 m/s
B.23 m/s and 22.4 m/s
C.23 m/s and 20.6 m/s
D.18 m/s and 20.6 m/s
MediumSolve

When a body moves with a constant speed along a circle

A.No work is done on it
B.No acceleration is produced in the body
C.No force acts on the body
D.Its velocity remains constant
EasySolve

Force $F$ on a particle moving in a straight line varies with distance $d$ as shown in the figure. The work done on the particle during its displacement of $12$ m is:

A.21 J
B.26 J
C.13 J
D.18 J
MediumSolve

A particle moves with a velocity $(5\hat i-3\hat j+6\hat k)\text{ ms}^{-1}$ horizontally under the action of a constant force $(10\hat i+10\hat j+20\hat k)\text{ N}$. The instantaneous power supplied to the particle is:

A.200 W
B.zero
C.100 W
D.140 W
EasySolve

In a circus stuntman rides a motorbike in a circular track of radius $R$ in the vertical plane. The minimum speed at highest point of track will be:

A.$\sqrt{2gR}$
B.$2gR$
C.$\sqrt{3gR}$
D.$\sqrt{gR}$
EasySolve

The minimum work done in pulling up a block of wood weighing $2 \text{ kN}$ for a length of $10 \text{ m}$ on a smooth plane inclined at an angle of $15^\circ$ with the horizontal is (given $\sin 15^\circ = 0.2588$):

A.$4.36 \text{ kJ}$
B.$5.17 \text{ kJ}$
C.$8.91 \text{ kJ}$
D.$9.82 \text{ kJ}$
EasySolve

A man fires a bullet of mass $200 \text{ g}$ at a speed of $5 \text{ m/s}$. The gun is of one kg mass. By what velocity the gun rebounds backwards?

A.$0.1 \text{ m/s}$
B.$10 \text{ m/s}$
C.$1 \text{ m/s}$
D.$0.01 \text{ m/s}$
EasySolve

This neet physics practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice physics sets →