Consider a particle moving along the x-axis where x(t) is the position of the particle at time t A particle, initially at rest, moves along the x-axis such that its acceleration at time t > 0 is given by a(t)=5cos(t). At t=0, its position is x=2?

(a) Find the velocity and position functions for the particle.

v(t)=
f(t)=

(b) Find the values of t for which the particle is at rest. (Use k as an arbitrary non-negative integer.)

t=

Answer 1

# v=5sint #
# x=-5cost+7#

At rest when # t = npi# where #n in NN#

#a=(dv)/dt and v=dx/dt # so with #a(t)=5cost# we have:
#\ \ \ \ \ (dv)/dt = 5cost# #:. v=5sint+A#
#v=0# when #t=0# (initially at rest); so
# \ \ \ \ \ 0 = 0+A => A=0# # :. v=5sint #

So then:

#\ \ \ \ \ (dx)/dt = 5sint# #:. x=-5cost+B#
#x=2# when #t=0#; so
# \ \ \ \ \ 2 = -5+B => B=7# #:. x=-5cost+7#
If the particle is at rest then #v=0#
# :. 5sint = 0# # :. sint = 0# # :. t = npi# where #n in NN#

Note: Some tutors and texts combine the initial conditions into a definite integral and remove the need to evaluate the constant of integration, as follows: e.g for the velocity we have:

# (dv)/dt = 5cost => int (dv)/dt dt=int5costdt#
If we combine the initial conditions into a definite integral then the integration variable #t# is arbitrary, then we can write
# int_0^v (dv)/dt dt=int_0^t 5costdt# # :. int_0^v dv=int_0^t 5costdt# (or if you prefer #int_0^v d rho=int_0^t 5costau d tau#) # :. [v]_0^v= [5sint]_0^t# # :. v-0= 5sint - 5sin0# # :. v= 5sint #, as before

Similarly for the displacement we could write

# int_2^x dx= int_0^t 5sint #, as before

and again we get the same solution.

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Answer 2

To find the position function ( x(t) ) of the particle, we'll integrate the given acceleration function ( a(t) = 5 \cos(t) ) twice with respect to time to obtain the position function.

Given: Initial velocity ( v(0) = 0 ) (particle is initially at rest) Initial position ( x(0) = 2 )

We start by integrating the acceleration function to find the velocity function: [ v(t) = \int a(t) , dt = \int 5\cos(t) , dt = 5\sin(t) + C_1 ]

Using the initial condition ( v(0) = 0 ), we find ( C_1 = 0 ), so the velocity function becomes: [ v(t) = 5\sin(t) ]

Next, we integrate the velocity function to find the position function: [ x(t) = \int v(t) , dt = \int 5\sin(t) , dt = -5\cos(t) + C_2 ]

Using the initial condition ( x(0) = 2 ), we find ( C_2 = 2 ), so the position function becomes: [ x(t) = -5\cos(t) + 2 ]

Therefore, the position function of the particle moving along the x-axis is: [ x(t) = -5\cos(t) + 2 ]

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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