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16. (JEE Main 2021 (Online) 25th February Evening Shift)

The point A moves with a uniform speed along the circumference of a circle of radius 0.36 m and covers 30 in 0.1 s. The perpendicular projection 'P' from 'A' on the diameter MN represents the simple harmonic motion of 'P'. The restoration force per unit mass when P touches M will be :

JEE Main 2021 (Online) 25th February Evening Shift Physics - Simple Harmonic Motion Question 72 English

A. 9.87 N

B. 0.49 N

C. 50 N

D. 100 N

Correct Answer is Option (A)

JEE Main 2021 (Online) 25th February Evening Shift Physics - Simple Harmonic Motion Question 72 English Explanation
The point a covers 30 in 0.1 sec.

Means π 6 0.1 sec.

1 0.1 π 6

2 π 0.1 × 6 π × 2 π

T = 1.2 sec.

We know that ω = 2 π T

ω = 2 π 1.2

Restoration force ( F ) = m ω 2 A

Then Restoration force per unit mass ( F m ) = ω 2 A

( F m ) = ( 2 π 1.2 ) 2 × 0.36

9.87 N

17. (JEE Main 2021 (Online) 24th February Evening Shift)

When a particle executes SHM, the nature of graphical representation of velocity as a function of displacement is :

A. circular

B. straight line

C. parabolic

D. elliptical

Correct Answer is Option (D)

Since, the particle is executing SHM.

Therefore, displacement equation of wave will be

y = A sin ω t

y / A = sin ω t

and wave velocity equation will be

v y = d y d t = A ω cos ω t

v y / A ω = cos ω t

Now, sin 2 ω t + cos 2 ω t = 1

( y / A ) 2 + ( v y / A ω ) 2 = 1

This equation is similar to the equation of ellipse.

18.(JEE Main 2021 (Online) 27th July Evening Shift )

A particle executes simple harmonic motion represented by displacement function as

x(t) = A sin( ω t + ϕ )

If the position and velocity of the particle at t = 0 s are 2 cm and 2 ω cm s 1 respectively, then its amplitude is x 2 cm where the value of x is _________________.

Correct Answer is (2)

x(t) = A sin( ω t + ϕ )

v(t) = A ω cos ( ω t + ϕ )

2 = A sin ϕ ...... (1)

2 ω = A ω cos ϕ ....... (2)

From (1) and (2)

tan ϕ = 1

ϕ = 45

Putting value of ϕ in equation (1),

2 = A { 1 2 }

A = 2 2

x = 2

19.(JEE Main 2021 (Online) 18th March Morning Shift )

A particle performs simple harmonic motion with a period of 2 second. The time taken by the particle to cover a displacement equal to half of its amplitude from the mean position is 1 a s. The value of 'a' to the nearest integer is _________.

Correct Answer is (6)

Time period (T) = 2 sec.

X = A sin ( ω t + ϕ ) ( ϕ = 0 at M.P.)

A 2 = A sin 2 π T t

2 π 2 t = π 6

t = 1 6

a = 6

20.(JEE Main 2021 (Online) 26th February Evening Shift )

A particle executes S.H.M. with amplitude 'a', and time period 'T'. The displacement of the particle when its speed is half of maximum speed is x a 2 . The value of x is __________.

Correct Answer is (3)

For a particle executes S.H.M.

V = ω a 2 x 2

Given, V = V max 2 = A ω 2

A 2 ω 2 4 = ω 2 a 2 ω 2 x 2

x = 3 2 a