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Simple M1 Question

I know that the modulus of a force is 25. tsrhelp.jpg

How do I find the acute angle? I know that this would be the angle between the y axis and the force.

In the mark scheme they did Tan^-1(3/4). Which is OK, but the modulus of these would be 5, not 25.
Interesting. I get 5 as well.
Reply 2
Avatar for Alex-Torres
Alex-Torres
OP
15
Original post by keromedic
Interesting. I get 5 as well.

Here is the mark scheme to the question - http://www.tomred.org/uploads/7/7/8/3/778329/m1_ms_solomon_b.pdf - Q1
Original post by Alex-Torres
Here is the mark scheme to the question - http://www.tomred.org/uploads/7/7/8/3/778329/m1_ms_solomon_b.pdf - Q1

I agree with the angle, I guess, but not the magnitude.

But I'm terribly weak on mechanics so someone else may be better suited to help.
Reply 4
Avatar for Rock_Set
Rock_Set
2
Original post by Alex-Torres
I know that the modulus of a force is 25.


How do I find the acute angle? I know that this would be the angle between the y axis and the force.


In the mark scheme they did Tan^-1(3/4). Which is OK, but the modulus of these would be 5, not 25.


What did you get F as? I've done this question but we can't post solutions.

Just a reminder tan−1(15/20)=tan−1(3/4) tan^{-1}(15/20) = tan^{-1}(3/4) , also acute angle doesn't always have to be between a force and y-axis, it could be between a force and the x-axis.
(edited 10 years ago)
Reply 5
Avatar for davros
davros
16
Original post by Alex-Torres
I know that the modulus of a force is 25. tsrhelp.jpg

How do I find the acute angle? I know that this would be the angle between the y axis and the force.

In the mark scheme they did Tan^-1(3/4). Which is OK, but the modulus of these would be 5, not 25.



Original post by keromedic
I agree with the angle, I guess, but not the magnitude.

But I'm terribly weak on mechanics so someone else may be better suited to help.


I'm not sure what the confusion is.

5 is the magnitude of the acceleration.

F = ma and m = 5 so magnitude of force = 25.

The force and acceleration are vectors in the same direction - it doesn't matter if they have magnitude 5, 25 or 125, the angle will still be the same - you're just working with some scaled version of the standard (3,4,5) triangle :smile:
Original post by davros
I'm not sure what the confusion is.

5 is the magnitude of the acceleration.

F = ma and m = 5 so magnitude of force = 25.

The force and acceleration are vectors in the same direction - it doesn't matter if they have magnitude 5, 25 or 125, the angle will still be the same - you're just working with some scaled version of the standard (3,4,5) triangle :smile:

:facepalm:
Of course.

I really need to stay clear of mechanics from now on. I can only do it myself.
Reply 7
Avatar for Alex-Torres
Alex-Torres
OP
15
Original post by davros
I'm not sure what the confusion is.

5 is the magnitude of the acceleration.

F = ma and m = 5 so magnitude of force = 25.

The force and acceleration are vectors in the same direction - it doesn't matter if they have magnitude 5, 25 or 125, the angle will still be the same - you're just working with some scaled version of the standard (3,4,5) triangle :smile:

Thanks - makes sense now!
Reply 8
Avatar for Alex-Torres
Alex-Torres
OP
15
Original post by davros
I'm not sure what the confusion is.

5 is the magnitude of the acceleration.

F = ma and m = 5 so magnitude of force = 25.

The force and acceleration are vectors in the same direction - it doesn't matter if they have magnitude 5, 25 or 125, the angle will still be the same - you're just working with some scaled version of the standard (3,4,5) triangle :smile:

tsrrealy.jpgHow would I do part b? I''m stuck - I know that the mod of 6i+2j is 2root10, as asked. But I don't know how you'd get to 6i+2j?

Edit: figured it out now!
(edited 10 years ago)

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