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Calculate the magnitude of particle acceleration

1. Homework Statement

A particles position is given by r=42t^2i + 41t^3j + 6k. Calculate the magnitude of its acceleration at time t = 15 seconds

2. Homework Equations



3. The Attempt at a Solution

to find the acceleration i found the second derivative which i had as 246t + 84. Then i put 15 in as t and got 3774, but according to the answers i should get 3691. What did i do wrong
 

Answers and Replies

Doc Al
Mentor
44,828
1,084
You are dealing with vectors. The acceleration is 246tj + 84i, not just 246t + 84.
 
but do i still have to find the second derivative using this? Can you give me a hint on how to do this?
 
ive worked this one out. Thanks for the hint
 

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