Mechanics
Can someone explain how the answer is 7.5N I've attached the question and my workings.
Original post by Hollymae764
Can someone explain how the answer is 7.5N I've attached the question and my workings.
They're just using ,mass x acceleration.
I don't think there's anything subtle in the question
ETA: when they say "resultant force" they mean the sum of all forces acting, so there's no other calculation to be done!
(edited 3 years ago)
Original post by davros
They're just using ,mass x acceleration.
I don't think there's anything subtle in the question
I don't think there's anything subtle in the question
So how do I know hen I need to use mass x acceleration and not Newton's First Law?
Original post by Hollymae764
Ignore that Stupid question 
Stupid question So why do I not take into account the weight of the particle and the force of gravity?
Original post by Hollymae764
So how do I know hen I need to use mass x acceleration and not Newton's First Law?
You're using Newton's Second Law
F = ma
where F is the resultant force and a is the acceleration.
There could be any number of individual forces that we don't know about (rocket motor, magnetism, tension etc) - the point is that we only want to know the resultant (i.e. total) force on the particle producing that final acceleration.
Original post by Hollymae764
So why do I not take into account the weight of the particle and the force of gravity?
I know what you mean - but you're overthinking the question!
It's the same question as "a particle of mass m moves with acceleration a - what is the applied force on it?"
Original post by davros
You're using Newton's Second Law
F = ma
where F is the resultant force and a is the acceleration.
There could be any number of individual forces that we don't know about (rocket motor, magnetism, tension etc) - the point is that we only want to know the resultant (i.e. total) force on the particle producing that final acceleration.
F = ma
where F is the resultant force and a is the acceleration.
There could be any number of individual forces that we don't know about (rocket motor, magnetism, tension etc) - the point is that we only want to know the resultant (i.e. total) force on the particle producing that final acceleration.
Ah that makes sense now thank you
Original post by Hollymae764
Ah that makes sense now thank you
no problem
For a 1-mark question they're not going be asking anything too complicated!Quick Reply
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