# Vectors - Displacement to Accelleration

• cryodynamics

## Homework Statement

An object moves with its position obeying x=5t^2-6t^2 and y=3t^-1+4t^4. What is the magnitude of its acceleration at t=1s;
a)57 m/s^2
b)34 m/s^2
c)26 m/s^2
d)44 m/s^2
e)0 m/s^2

x=5t^3-6t^2
y=3t^-1+4t^4

## The Attempt at a Solution

Second derivative of the displacement x is;
ax=30t-12 m/s^2
Second derivative of the displacement y is;
ay=8t m/s^2

t=1 -> ax
ax = 18

t=1 -> ay
ay = 8

Resultant acceleration = sqrt(18^2+8^2) = 19.69

Which is wrong according to the answer I found online which was a) 57 m/s^2. Anyone show me where I've messed up or is the answer I found wrong?

Last edited:

## Homework Statement

An object moves with its position obeying x=5t^2-6t^2 and y=3t^-1+4t^4. What is the magnitude of its acceleration at t=1s;
a)57 m/s^2
b)34 m/s^2
c)26 m/s^2
d)44 m/s^2
e)0 m/s^2

x=5t^2-6t^2
y=3t^-1+4t^4

## The Attempt at a Solution

Second derivative of the displacement x is;
ax=30t-12 m/s^2
Second derivative of the displacement y is;
ay=8t m/s^2

t=1 -> ax
ax = 18

t=1 -> ay
ay = 8

Resultant acceleration = sqrt(18^2+8^2) = 19.69

Which is wrong according to the answer I found online which was a) 57 m/s^2. Anyone show me where I've messed up or is the answer I found wrong?

The x expressions don't match up, but I guess you actually meant x=5t^3-6t^2

I can't imagine what you thought the y expression was ??

The x expressions don't match up, but I guess you actually meant x=5t^3-6t^2

I can't imagine what you thought the y expression was ??

Ahh yes sorry about that, I'll fix that up. What do you mean by 'I can't imagine what you thought the y expression was?' That equation for y is the exact one given?

Can you check that

x=5t^2-6t^2 and y=3t^-1+4t^4

are correct.

x=5t3-6t2
y=3t-1+4t4
Are the the correct equations given in the question.

x=5t3-6t2
y=3t-1+4t4
Are the the correct equations given in the question.

OK .. if that is the expression for y, then 8t is not the second derivative.

OK .. if that is the expression for y, then 8t is not the second derivative.

Ahh I got the answer this time, my problem was I thought I could simplify y=3t-1+4t4 to 4t3/3 I now realize what a rookie error that was lol. Thanks for your help everyone.