M1 question help! Watch

Reshyna
  • Political Ambassador
Badges: 15
Rep:
?
#1
Report Thread starter 2 years ago
#1
Bill walks 4km due west from O to A and then 5km in a north-east direction from A to B. Find the distance of B from O.
I am getting the answer as 3km but the answer in the book is 3.57km. How could that answer come? Any ideas anyone?
0
reply
nerak99
Badges: 11
Rep:
?
#2
Report 2 years ago
#2
Assuming that "carries a B" means "carries at B" and there is an upward force at A when it is not zero.

"The answers given come from the eq 50(1.44-x)^2=34.56(1.44-x)+115.2x+50x^2 with the 34.56 term removed for part ii.

I am not sure of the wording of what you have given us (What does "last one" mean?)

I think that for M1 we would have to use that the maximum force at A will occur when the support X is at B in which case the force at A will be 25 (using moments about B). The force at X will be (using Sigma Fy=0 for equilibrium) 40+50-25=65.
0
reply
Reshyna
  • Political Ambassador
Badges: 15
Rep:
?
#3
Report Thread starter 2 years ago
#3
(Original post by nerak99)
Assuming that "carries a B" means "carries at B" and there is an upward force at A when it is not zero.

"The answers given come from the eq 50(1.44-x)^2=34.56(1.44-x)+115.2x+50x^2 with the 34.56 term removed for part ii.

I am not sure of the wording of what you have given us (What does "last one" mean?)

I think that for M1 we would have to use that the maximum force at A will occur when the support X is at B in which case the force at A will be 25 (using moments about B). The force at X will be (using Sigma Fy=0 for equilibrium) 40+50-25=65.
the last one was actually meaning the last sentence, that's it. Thanks for helping me.
0
reply
nerak99
Badges: 11
Rep:
?
#4
Report 2 years ago
#4
(Original post by Rashina)
the last one was actually meaning the last sentence, that's it. Thanks for helping me.
Hey! Don't delete a question using edit like that because it makes the answer useless for anyone else. Raise a new question.
0
reply
nerak99
Badges: 11
Rep:
?
#5
Report 2 years ago
#5
(Original post by Rashina)
Bill walks 4km due west from O to A and then 5km in a north-east direction from A to B. Find the distance of B from O.
I am getting the answer as 3km but the answer in the book is 3.57km. How could that answer come? Any ideas anyone?
Looking at this as vectors we have

\begin{pmatrix} -4 + 5 \cos {45} \\0 + 5 \cos {45} \end{pmatrix}
Where the Cos 45 is due to splitting the NE direction into x and y components.
This equals
\begin{pmatrix} -0.4645 \\3.5355 \end{pmatrix}

and Pythagoras gives us 3.5659
0
reply
tiny hobbit
Badges: 15
Rep:
?
#6
Report 2 years ago
#6
(Original post by Rashina)
Bill walks 4km due west from O to A and then 5km in a north-east direction from A to B. Find the distance of B from O.
I am getting the answer as 3km but the answer in the book is 3.57km. How could that answer come? Any ideas anyone?
Or use the cosine rule. Your answer suggests that you think that any triangle with sides 4 and 5 must be a 3,4,5 traingle. It depends on the angle between the sides.
0
reply
Reshyna
  • Political Ambassador
Badges: 15
Rep:
?
#7
Report Thread starter 2 years ago
#7
(Original post by nerak99)
Looking at this as vectors we have

\begin{pmatrix} -4 + 5 \cos {45} \\0 + 5 \cos {45} \end{pmatrix}
Where the Cos 45 is due to splitting the NE direction into x and y components.
This equals
\begin{pmatrix} -0.4645 \\3.5355 \end{pmatrix}

and Pythagoras gives us 3.5659
How do I find the direction of the displacement OB?
0
reply
nerak99
Badges: 11
Rep:
?
#8
Report 2 years ago
#8
Well assuming you want from North, the Vector is 0.4645 West (Cos it is negative), 3.5355 North. If you draw this as a Triangle the angle anticlockwise from North is atan (0.4645/3.5355).

As the other poster said, you could use the Cos rule which may suit the M1 syllabus. To me, this is over complicated but then I am very used to vectors for solving this kind of thing.
0
reply
Neil Capelli
Badges: 0
Rep:
?
#9
Report 2 years ago
#9
Desperately need help on this. Can anyone help please?

An object can slide on a path inclined at 15 degrees to the horizontal. It is acted on by a force of magnitude 50 N, acting at an angle of 5 degrees to the upward vertical, as shown in the diagram. Find the components of the force a) in directions parallel to and at right angles to the path b) in horizontal and vertical directions, c) in directions parallel to the path and horizontally, d) in directions at right angles to the path and horizontally, e) in directions parallel to the path and vertically f) in directions at right angles to the path and vertically.
0
reply
Reshyna
  • Political Ambassador
Badges: 15
Rep:
?
#10
Report Thread starter 2 years ago
#10
(Original post by Neil Capelli)
Desperately need help on this. Can anyone help please?

An object can slide on a path inclined at 15 degrees to the horizontal. It is acted on by a force of magnitude 50 N, acting at an angle of 5 degrees to the upward vertical, as shown in the diagram. Find the components of the force a) in directions parallel to and at right angles to the path b) in horizontal and vertical directions, c) in directions parallel to the path and horizontally, d) in directions at right angles to the path and horizontally, e) in directions parallel to the path and vertically f) in directions at right angles to the path and vertically.
You should probably post this in a separate thread made by you in the maths forum so that many people can view it. My question at the top is already answered so there are chances many people could ignore your question.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts

All the exam results help you need

2,750

people online now

225,530

students helped last year

University open days

  • University of Dundee
    Undergraduate Open Day Undergraduate
    Mon, 26 Aug '19
  • University of Aberdeen
    General Open Day Undergraduate
    Tue, 27 Aug '19
  • Norwich University of the Arts
    Postgraduate (MA) Open Day Postgraduate
    Sat, 31 Aug '19

How are you feeling about GCSE Results Day?

Hopeful (159)
13.29%
Excited (106)
8.86%
Worried (218)
18.23%
Terrified (280)
23.41%
Meh (96)
8.03%
Confused (32)
2.68%
Putting on a brave face (156)
13.04%
Impatient (149)
12.46%

Watched Threads

View All