runny4
Badges: 6
Rep:
?
#1
Report Thread starter 5 years ago
#1
http://www.mei.org.uk/files/papers/M1_Paper_Jan13.pdf
For the above above paper question 3iii, why couldn't you just resolve perpendicular to motion and say that there is a resultant force because Sam's and Tom's components aren't the same at right angles to motion. (the mark scheme is at the bottom of the pdf)
Also for question 7vi, i don't get whats going on

Thank you
0
reply
Zacken
Badges: 22
Rep:
?
#2
Report 5 years ago
#2
(Original post by runny4)
http://www.mei.org.uk/files/papers/M1_Paper_Jan13.pdf
For the above above paper question 3iii, why couldn't you just resolve perpendicular to motion and say that there is a resultant force because Sam's and Tom's components aren't the same at right angles to motion. (the mark scheme is at the bottom of the pdf)
Uh, you can? I think - it's a fine argument. There's a component of force acting at right-angles to the motion, hence the resultant force will not be in the direction of the motion.


Also for question 7vi, i don't get whats going on

Thank you
The part of the string BC is 2.3 metres which is greater than 2 metres, i.e: it is "too long" and the piece BC will be effectively useless. Imagine holding a block using a chain/string that is 2 metres long when the block is situated one metre away from you, the chain/string will be pretty much useless, it'll be just limp (slack) and doing nothing. That's the case here: the piece AB will have to handle the entirety of the weight (50N) and you'll find that the angle CAB is 90 degrees, so it's basically just resolve upwards/downwards to get AC = 50 N and BC = 0 / useless.
0
reply
runny4
Badges: 6
Rep:
?
#3
Report Thread starter 5 years ago
#3
(Original post by Zacken)
Uh, you can? I think - it's a fine argument. There's a component of force acting at right-angles to the motion, hence the resultant force will not be in the direction of the motion.




The part of the string BC is 2.3 metres which is greater than 2 metres, i.e: it is "too long" and the piece BC will be effectively useless. Imagine holding a block using a chain/string that is 2 metres long when the block is situated one metre away from you, the chain/string will be pretty much useless, it'll be just limp (slack) and doing nothing. That's the case here: the piece AB will have to handle the entirety of the weight (50N) and you'll find that the angle CAB is 90 degrees, so it's basically just resolve upwards/downwards to get AC = 50 N and BC = 0 / useless.
Just for the 2nd question if you use the cosine rule to find angle CAB, you get
(4+0.25-2.3^2)/(2*2*0.5)= cos(CAB) but this does not give you CAB=90
0
reply
Zacken
Badges: 22
Rep:
?
#4
Report 5 years ago
#4
(Original post by runny4)
Just for the 2nd question if you use the cosine rule to find angle CAB, you get
(4+0.25-2.3^2)/(2*2*0.5)= cos(CAB) but this does not give you CAB=90
Right, but if you're using the cosine rule like that, then you're assuming BC is taut when it isn't.
0
reply
runny4
Badges: 6
Rep:
?
#5
Report Thread starter 5 years ago
#5
(Original post by Zacken)
Right, but if you're using the cosine rule like that, then you're assuming BC is taut when it isn't.
Then how would you deduce that Angle CAB is 90 degrees?
0
reply
ghostwalker
  • Study Helper
Badges: 17
#6
Report 5 years ago
#6
(Original post by runny4)
http://www.mei.org.uk/files/papers/M1_Paper_Jan13.pdf
For the above above paper question 3iii, why couldn't you just resolve perpendicular to motion and say that there is a resultant force because Sam's and Tom's components aren't the same at right angles to motion. (the mark scheme is at the bottom of the pdf)
IMO, saying there is a resultant force perpendicular to the acceleration isn't sufficient. There must be something counteracting that resultant force for the car to accelerate as it does. I.e. a resistive force perpendicular to the motion.
0
reply
runny4
Badges: 6
Rep:
?
#7
Report Thread starter 5 years ago
#7
(Original post by ghostwalker)
IMO, saying there is a resultant force perpendicular to the acceleration isn't sufficient. There must be something counteracting that resultant force for the car to accelerate as it does. I.e. a resistive force perpendicular to the motion.
but its asking why the resultant of the forces exerted by Sam and Tom is not in the direction of the car’s acceleration not why the car travels in a straight line
0
reply
ghostwalker
  • Study Helper
Badges: 17
#8
Report 5 years ago
#8
(Original post by runny4)
but its asking why the resultant of the forces exerted by Sam and Tom is not in the direction of the car’s acceleration not why the car travels in a straight line
it's not about why the car travels in a straight line.

Your answer is only showing that the sum of the perpendicular components of the forces (of the two people) is non-zero. This does not explain why the car moves in the direction it does.

The car will accelerate in the direction of the sum of the forces acting on it - always. The question is asking why is this direction different to the resultant of the forces exerted by the two people.
0
reply
runny4
Badges: 6
Rep:
?
#9
Report Thread starter 5 years ago
#9
(Original post by ghostwalker)
it's not about why the car travels in a straight line.

Your answer is only showing that the sum of the perpendicular components of the forces (of the two people) is non-zero. This does not explain why the car moves in the direction it does.

The car will accelerate in the direction of the sum of the forces acting on it - always. The question is asking why is this direction different to the resultant of the forces exerted by the two people.
ok thanks
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Poll: What factors affect your mental health most right now? Post-lockdown edition

Anxiousness about restrictions easing (30)
5.32%
Uncertainty around my education (65)
11.52%
Uncertainty around my future career prospects (66)
11.7%
Lack of purpose or motivation (75)
13.3%
Lack of support system (eg. teachers, counsellors, delays in care) (32)
5.67%
Impact lockdown had on physical health (28)
4.96%
Social worries (incl. loneliness/making friends) (60)
10.64%
Financial worries (35)
6.21%
Concern about myself or my loves ones getting/having been ill (22)
3.9%
Exposure to negative news/social media (34)
6.03%
Difficulty accessing real life entertainment (15)
2.66%
Lack of confidence in making big life decisions (56)
9.93%
Worry about missed opportunities during the pandemic (46)
8.16%

Watched Threads

View All