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Circular Motion question

2024 · 8 Apr · Shift 1 · Q66
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  5. /2024 · 8 Apr · Shift 1 · Q66

Circular Motion question

2024 · 8 Apr · Shift 1 · Q66

JEE MainPhysicsCircular MotionMCQ+4 / −1
A clock has 75 cm,60 cm75 \mathrm{~cm}, 60 \mathrm{~cm}75 cm,60 cm long second hand and minute hand respectively. In 30 minutes duration the tip of second hand will travel xxx distance more than the tip of minute hand. The value of xxx in meter is nearly (Take π=3.14\pi=3.14π=3.14) :
  1. A
    118.9
  2. B
    140.5
  3. C
    139.4
  4. D
    220.0
View written solutionFree

Correct answer: C

  1. Given data
  • Length of second hand: rs=75 cm=0.75 mr_s = 75\text{ cm} = 0.75\text{ m}rs​=75 cm=0.75 m
  • Length of minute hand: rm=60 cm=0.60 mr_m = 60\text{ cm} = 0.60\text{ m}rm​=60 cm=0.60 m
  • Time interval: 303030 minutes
  • Take π=3.14\pi = 3.14π=3.14

We need the extra distance traveled by the tip of the second hand compared to the tip of the minute hand in 303030 minutes.


  1. Distance traveled by tip = number of revolutions ×\times× circumference

For a hand of length rrr, one full revolution covers: 2πr2\pi r2πr


  1. Second hand distance in 30 minutes

The second hand completes 1 revolution per minute.

So in 303030 minutes, number of revolutions: ns=30n_s = 30ns​=30

Distance traveled: ds=30×2π×0.75d_s = 30 \times 2\pi \times 0.75ds​=30×2π×0.75 ds=30×2×3.14×0.75d_s = 30 \times 2 \times 3.14 \times 0.75ds​=30×2×3.14×0.75 ds=30×4.71d_s = 30 \times 4.71ds​=30×4.71 ds=141.3 md_s = 141.3\text{ m}ds​=141.3 m


  1. Minute hand distance in 30 minutes

The minute hand completes 1 revolution in 60 minutes.

So in 303030 minutes, number of revolutions: nm=3060=12n_m = \frac{30}{60} = \frac{1}{2}nm​=6030​=21​

Distance traveled: dm=12×2π×0.60d_m = \frac{1}{2} \times 2\pi \times 0.60dm​=21​×2π×0.60 dm=π×0.60d_m = \pi \times 0.60dm​=π×0.60 dm=3.14×0.60d_m = 3.14 \times 0.60dm​=3.14×0.60 dm=1.884 md_m = 1.884\text{ m}dm​=1.884 m


  1. Required extra distance

x=ds−dmx = d_s - d_mx=ds​−dm​ x=141.3−1.884x = 141.3 - 1.884x=141.3−1.884 x=139.416 mx = 139.416\text{ m}x=139.416 m

Nearly, x≈139.4 mx \approx 139.4\text{ m}x≈139.4 m


  1. Option matching

The nearest option is: C: 139.4\boxed{\text{C: } 139.4}C: 139.4​


  1. Comparison with stored answer

Stored correct answer: C

Our derived answer: C

So, the answer agrees with the stored answer.

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