The displacement y of a particle executing simple harmonic motion is given by the equation:
y=4sin(0.2t+0.3)
This equation is in the standard form y=Asin(ωt+ϕ), where:
• A is the amplitude
• ω is the angular frequency
• ϕ is the phase constant
From the given equation, we can identify:
Amplitude, A=4 m
Angular frequency, ω=0.2 rad/s
Phase constant, ϕ=0.3 rad
(i) Calculate the angular frequency, the frequency, period and phase of the motion.
Step 1: Identify the angular frequency.
From the equation, the angular frequency is directly given.
ω=0.2rad/s
The angular frequency is 0.2rad/s.
Step 2: Calculate the frequency (f).
The frequency is related to the angular frequency by the formula f=2πω.
f=2πrad0.2rad/s
f=π0.1Hz
f≈3.141590.1Hz
f≈0.0318Hz
The frequency is 0.0318Hz.
Step 3: Calculate the period (T).
The period is the reciprocal of the frequency, T=f1, or can be calculated as T=ω2π.
T=0.2rad/s2πrad
T=10πs
T≈10×3.14159s
T≈31.4s
The period is 31.4s.
Step 4: Identify the phase of the motion.
The phase constant (or initial phase) is directly given in the equation.
ϕ=0.3rad
The phase is 0.3rad.
(ii) Calculate the initial velocity and acceleration of the particle.
Step 1: Find the general expression for velocity (v).
Velocity is the first derivative of displacement with respect to time.
v=dtdy=dtd[Asin(ωt+ϕ)]
v=Aωcos(ωt+ϕ)
Substitute the values:
v=(4m)(0.2rad/s)cos(0.2t+0.3)
v=0.8cos(0.2t+0.3)m/s
Step 2: Calculate the initial velocity (v0) at t=0.
v0=0.8cos(0.2(0)+0.3)
v0=0.8cos(0.3)m/s
Using cos(0.3rad)≈0.9553:
v0≈0.8×0.9553m/s
v0≈0.764m/s
The initial velocity is 0.764m/s.
Step 3: Find the general expression for acceleration (a).
Acceleration is the first derivative of velocity with respect to time.
a=dtdv=dtd[Aωcos(ωt+ϕ)]
a=−Aω2sin(ωt+ϕ)
Substitute the values:
a=−(4m)(0.2rad/s)2sin(0.2t+0.3)
a=−4×0.04sin(0.2t+0.3)m/s2
a=−0.16sin(0.2t+0.3)m/s2
Step 4: Calculate the initial acceleration (a0) at t=0.
a0=−0.16sin(0.2(0)+0.3)
a0=−0.16sin(0.3)m/s2
Using sin(0.3rad)≈0.2955:
a0≈−0.16×0.2955m/s2
a0≈−0.0473m/s2
The initial acceleration is −0.0473m/s2.
(iii) Calculate the maximum velocity and acceleration.
Step 1: Calculate the maximum velocity (vmax).
The maximum velocity occurs when cos(ωt+ϕ)=±1.
vmax=Aω
vmax=(4m)(0.2rad/s)
vmax=0.8m/s
The maximum velocity is 0.8m/s.
Step 2: Calculate the maximum acceleration (amax).
The maximum acceleration occurs when sin(ωt+ϕ)=±1.
amax=Aω2
amax=(4m)(0.2rad/s)2
amax=4×0.04m/s2
amax=0.16m/s2
The maximum acceleration is 0.16m/s2.