Physics Problems ? (particle acceleration)

[JJ91284]

Physics Problems ? (particle acceleration)

I'm working on my last 2 of 30 or so physics problems and am pretty lost on what to do/how to even start. The homework is due in exactly 3 hrs, I already have an "A" on this assignment but would like to squeeze on these last 6 points or so.

Question 6

A particle experiences a constant acceleration that is north at 100 m/s2. At t = 0, its velocity vector is 45 m/s east. At what time will the magnitude of the velocity be 100 m/s?



Question 7


An accelerometer-a device to measure acceleration-can be as simple as a small pendulum. Suppose you are flying a small plane in a straight horizontal line and your accelerometer hangs 11° behind the vertical, opposite the direction of motion. What is your acceleration?

 

[Kurdt]

What are your thoughts so far?

Hints:

Qu #6: You're given the component of velocity in the east direction and the magnitude of the velocity at a certain time, how can you work out the north component?

Qu #7: Draw a free body diagram of the pendulum and see if you can work from there.

 

[JJ91284]

Question 6 I don't really understand what they are trying to get across.

So a particle is going N at 100 ms^2

So that gives me acceleration is=100 constantly

It gives me east velocity at 45 m/s at t=0 (time)


I'm assuming the North part is important, but I don't know what equation they're looking for or what in general I'm suppose to find.


As far as question 7 goes, am I suppose to use gravity (9.8 m/s2) for anything. The plane is obviously accelerating because the pendulum is back 11 degrees. Just like when a car accelerates, your pushed into the seat.

I was thinking of accelerating formulas I know, and a=v/t doesn't work. I don't have velocity or time. The only component that I feel I have would be the angle which is 11 degrees. Which I don't know what I'm suppose to use that for.

 

[JJ91284]

I guess there were a lot of students confused on question 7 so this is what are instructor said.

HW problems from Chapter 3 Hint for Problem 7: The tension on the pendulum string has an x and y component, the y component is T cos theta and is equal to mg - use this to solve for T. The x component is balanced by the forward acceleration of the airplane - so use T sin theta - a*m to find a.

I'm going to see if I can figure it out now.

 

[Kurdt]

Stick with 6 for now. What do you know about vectors, their components and their magnitudes? That is all you really need to solve this question. The following page may also help.

http://hyperphysics.phy-astr.gsu.edu/hbase/vect.html

 

[mezarashi]

Acceleration vectors can be added together using the same math as you've been using to add velocity vectors. You do not need to really break the components up into x-y, because you already know the direction of the acceleration!

1. Due to gravity directly down (-y).
2. Due to the plane directly to the back (-x).