Physics Waves NUMS 2024
PMDC Verified Question 21 of 125
A body of mass 10 kg is connected to a spring and it is oscillating on a horizontal frictionless surface. If the maximum displacement of body is 20 cm and spring constant is 20 Nm\(^{-1}\). What is the acceleration of the body?
A
2.2 m s\(^{-1}\)
B
4 m s\(^{-1}\)
C
2 m s\(^{-1}\)
D
0.4 m s\(^{-1}\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: 0.4 m s\(^{-1}\)
Concept:

In Simple Harmonic Motion, maximum acceleration occurs at the points of maximum displacement (the amplitude), where the restoring force is strongest.

Formula:

$$ F = ma $$
$$ F = kx $$
$$ a = \frac{kx}{m} $$

Solution:

  • We are given: Mass \( m = 10 \text{ kg} \), Spring constant \( k = 20 \text{ N/m} \).


  • The maximum displacement (amplitude) is given in centimeters. Convert it to standard SI units (meters): \( x = 20 \text{ cm} = 0.2 \text{ m} \).


  • Plug the values into the acceleration formula:


  • \( a = \frac{20 \times 0.2}{10} \).


  • \( a = \frac{4}{10} = 0.4 \text{ m s}^{-1} \).


Why other options are incorrect:

Option B (4) happens if a student forgets to divide by the mass (10 kg). Option A and C result from not converting centimeters to meters.

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