MCQEasyJEE 2023Circular Motion Dynamics

JEE Physics 2023 Question with Solution

A vehicle of mass 200kg200 \, \text{kg} is moving along a levelled curved road of radius 70m70 \, \text{m} with angular velocity of 0.2rad/s0.2 \, \text{rad/s}. The centripetal force acting on the vehicle is:

  • A

    2800N2800 \, \text{N}

  • B

    560N560 \, \text{N}

  • C

    2240N2240 \, \text{N}

  • D

    14N14 \, \text{N}

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: mass of the vehicle = 200kg200 \, \text{kg}, radius of the road = 70m70 \, \text{m}, angular velocity = 0.2rad/s0.2 \, \text{rad/s}.

Find: The centripetal force acting on the vehicle.

The centripetal force required to keep an object of mass mm moving in a circular path of radius rr with angular velocity ω\omega is given by

F=mω2rF = m\omega^2 r

Substituting the given values,

F=(200)(0.2)2(70)F = (200)(0.2)^2(70) F=200×0.04×70=560NF = 200 \times 0.04 \times 70 = 560 \, \text{N}

Therefore, the centripetal force acting on the vehicle is 560N560 \, \text{N}. The correct option is B.

Direct Substitution

Given: m=200kgm = 200 \, \text{kg}, ω=0.2rad/s\omega = 0.2 \, \text{rad/s}, r=70mr = 70 \, \text{m}.

Find: FcF_c.

Use the formula

Fc=mω2rF_c = m\omega^2 r

Now calculate the square of angular velocity first:

(0.2)2=0.04(0.2)^2 = 0.04

Then,

Fc=200×0.04×70F_c = 200 \times 0.04 \times 70 Fc=8×70=560NF_c = 8 \times 70 = 560 \, \text{N}

Thus, the centripetal force is 560N560 \, \text{N}.

Common mistakes

  • Using F=mωrF = m\omega r instead of F=mω2rF = m\omega^2 r. This is wrong because centripetal force depends on the square of angular velocity. Always square ω\omega before substitution.

  • Confusing linear speed with angular velocity. Here 0.2rad/s0.2 \, \text{rad/s} is already angular velocity, so there is no need to convert it before using F=mω2rF = m\omega^2 r.

  • Forgetting to include the radius rr in the formula. The expression for centripetal force in terms of angular velocity is F=mω2rF = m\omega^2 r, not only mω2m\omega^2.

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