# mechanics a level

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#1
hi, could i have some help pleaseeee, i am so confused
7. In this question, the unit vector i is horizontal and the unit vector j is vertically upwards. All forces are in newtons.

A small, heavy box is suspended in mid-air and is held in equilibrium by the tension in a light inextensible string and a horizontal force, as shown in the diagram.

The tension in the string is T1, where T1 = 30i + 49j. The horizontal force is F1, where F1 = pi.

(i) Write down the value of p and show that the mass of the box is 5 kg. [3]

(ii) Calculate the magnitude of T1 and the angle that T1 makes with the horizontal.
[3]
Another force F2 = 48i – 87j is now applied to the box. The force F1 still acts and the box is still in equilibrium.

(iii) The new tension in the string is T2 = ai + bj. Calculate the values of a and b. [2]
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#2
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1 year ago
#3
(Original post by dazedconfused)
Have you tried equating i components, then j components?
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#4
(Original post by Muttley79)
Have you tried equating i components, then j components?
for part i??
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1 year ago
#5
(Original post by dazedconfused)
for part i??
Yes
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#6
(Original post by Muttley79)
Yes
i feel really annoying but could you please explain by what you mean when you say equating the i and j components?? i would appereciate it alot
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1 year ago
#7
(Original post by dazedconfused)
i feel really annoying but could you please explain by what you mean when you say equating the i and j components?? i would appereciate it alot
The tension in the string is T1, where T1 = 30i + 49j. The horizontal force is F1, where F1 = pi.

I can't do it for you, it's against the rules, but put the i part of T1 = to the i part of F1.

Then the j component must equal what other force?
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#8
(Original post by Muttley79)
The tension in the string is T1, where T1 = 30i + 49j. The horizontal force is F1, where F1 = pi.

I can't do it for you, it's against the rules, but put the i part of T1 = to the i part of F1.

Then the j component must equal what other force?
OHHHH then j is vertical force which is the weight
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#9
(Original post by dazedconfused)
OHHHH then j is vertical force which is the mass
how had i not seen this omg thank you, i've actually done the rest of the questions, thank youuuu for your help
2
2 months ago
#10
(Original post by dazedconfused)
how had i not seen this omg thank you, i've actually done the rest of the questions, thank youuuu for your help
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2 months ago
#11
(Original post by stephja2004)
This thread is a year old, but have you followed the hints given above to answer the first part?
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