hayley26
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Hi, I am REALLY struggling on this question and dont know where to even begin, any help would be great!

The horizontal unit vectors i and j are in the directions east and north respectively.

A model ship of mass 2kg is moving so that its acceleration vector ams^-2 at time t seconds is given by

a=3(2t-5)i+4j. When t=T, the magnitude of the horizontal force acting on the ship is 10N.

Find the possible values of T.

Ive been told to use pythagorus to find the magnitude of the corresponding force and equate to 10 and solve for T. But unfortunately I do not know what that means so if someone could explain in simpler terms it would be much appreciated!!!! <3
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davros
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(Original post by hayley26)
Hi, I am REALLY struggling on this question and dont know where to even begin, any help would be great!

The horizontal unit vectors i and j are in the directions east and north respectively.

A model ship of mass 2kg is moving so that its acceleration vector ams^-2 at time t seconds is given by

a=3(2t-5)i+4j. When t=T, the magnitude of the horizontal force acting on the ship is 10N.

Find the possible values of T.

Ive been told to use pythagorus to find the magnitude of the corresponding force and equate to 10 and solve for T. But unfortunately I do not know what that means so if someone could explain in simpler terms it would be much appreciated!!!! <3
Force = mass x acceleration. If you have the magnitude of the force you can find the magnitude of acceleration. How do you get the magnitude of a vector when you know its i- and j- compnents?
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hayley26
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using pythagorus - but when finding magnitude e.g. (sqr root) (6t-15)^2 + 4^2 , do i ignore the t ?
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mqb2766
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(Original post by hayley26)
using pythagorus - but when finding magnitude e.g. (sqr root) (6t-15)^2 + 4^2 , do i ignore the t ?
The problem is to solve for the time when the acceleration corresponds to a force of 10N.
How are force and acceleration related? Then solve for t.

Note, your pythagorean triples could give you a short cut way to the answer(s), but setting up the problem as a quadratic in t is the usual method.
Last edited by mqb2766; 3 weeks ago
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