Tangential and normal components

[teng125]

a particle A is constrained to move in the circular slot of CD.knowing that t=0 the particle A starts from rest and moves so that its speed increases at a constant rate of 0.8in/s^2.Determine the magnitude of its total acceleration when t=2.pls help...

thanx...

 

[teng125]

ah,miss out smtg about the radius is 3.5in

 

[teng125]

i have no idea about it .pls help...

 

[teng125]

the answer is 1.048in

 

[Hootenanny]

Do you know how to do it or do you still need help?

 

[teng125]

no,i don't know how to do it.those replies are things that i have missed to type

 

[Doc Al]

Hints:
(1) The tangential component is given.
(2) The radial component is also known as centripetal acceleration.

 

[teng125]

i have got acc for tangential=0.8 , but the acc for normal i can't find because i don't know what is the velocity

 

[Hootenanny]

Is the acceleration centripetal or tangental?

 

[teng125]

the centripetal acc i can't find

 

[Doc Al]

What's the formula for centripetal acceleration?

 

[teng125]

acc(centripetal)=velocity^2 / radius

 

[Doc Al]

Good. So figure out the speed at t = 2 secs and you can calculate the centripetal component of the acceleration.

 

[teng125]

i still can't figure out

 

[Doc Al]

What's the speed at t = 2 seconds? (Hint: the tangential acceleration is constant so it's just uniformly accelerated motion.)

 

[teng125]

is it equals to zero??

 

[teng125]

oh...is it using the formula v=u + at ??

 

[Doc Al]

That's the one.

 

[teng125]

but then i got the velocity=1.6 and try to find the centripetal acc and then the total acc and got the wrong answer.did u get the correct answer??

 

[Doc Al]

Show your work.

(FYI: I believe you had a typo in your answer.)

 

[teng125]

for acc tangential=0.8 , for acc centripetal i use eqn v=u+at plus acc=v^2/R and obtain 0.7314
the acc total=1.5314 which is not the answer

 

[Doc Al]

The tangential and radial components are perpendicular components: you can't just add them. How do you find the magnitude of a vector given its components?

 

[teng125]

oh...i found it...thank you very much...