lolseriously?
Badges: 5
Rep:
?
#1
Report Thread starter 1 year ago
#1
A light see-saw is 10 m long with the pivot 3 m from the left.

(a)A 4 kg weight is placed on the left-hand end of the see-saw. Write down the anticlockwise moment about the pivot

(b)A force of magnitude F N is applied to the right-hand end of the see-saw. The force acts vertically downwards. Write down the clockwise moment about the pivot due to this weight.

(c)Find the value of F for which the system is in equilibrium

Sorta doubtful about my answers?
0
reply
ghostwalker
  • Study Helper
Badges: 17
#2
Report 1 year ago
#2
(Original post by lolseriously?)
A light see-saw is 10 m long with the pivot 3 m from the left.

(a)A 4 kg weight is placed on the left-hand end of the see-saw. Write down the anticlockwise moment about the pivot

(b)A force of magnitude F N is applied to the right-hand end of the see-saw. The force acts vertically downwards. Write down the clockwise moment about the pivot due to this weight.

(c)Find the value of F for which the system is in equilibrium

Sorta doubtful about my answers?
(a) 12g Nm

(b) 7F Nm

(c) F= 12g/7 N

You may need to evaluate those by putting in whatever appropriate value for g you're using.

If you get anything else, post working/thoughts.

Edit: I am assuming the see-saw remains horizontal.
Last edited by ghostwalker; 1 year ago
1
reply
lolseriously?
Badges: 5
Rep:
?
#3
Report Thread starter 1 year ago
#3
These are the other questions I was trying to get my head around but also sorta stuck on! Please help!

(2).Alice, who weighs 50 kg, sits on the right-hand end of a light see-saw. Bob, who weighs 80 kg, stands on the opposite side at a distance x m from the end. The length of the see-saw is 4 m and it pivots about its centre.

a). Draw a diagram showing the forces acting on the see-saw due to the two people. Label the value of each force in newtons. (2 marks)
b). Write down the total clockwise moment about the centre in terms of x. ( mark)
c). Find the value of x for which the see-saw is in equilibrium. ( 2 marks)
d). Given that Bob remains on the opposite side to Alice, describe with inequalities the range of x for which the see-saw tilts towards Alice. (2 marks)
e).Describe one limitation of this model. (1 mark)
3). A 5000 kg bus hangs 12 m over the edge of a cliff and has 1000 kg of gold at the front. The gold sits on a wheeled cart. A group of n people, each weighing 70 kg, stands at the other end. The bus is 20 m long.
a).Write down the total clockwise moment about the cliff edge in terms of n. (7 marks)
b).Find the smallest number of people needed to stop the bus falling over the cliff. (2 marks)

c).One person needs to walk to the end of the bus to retrieve the gold. Find the smallest number of people needed to stop the bus falling over the cliff in this situation, including the one retrieving the gold. (4 marks)
4). Two identical 5 m light see-saws are joined at their ends. Robert, who weighs 80 kg, stands on top of the joint. The distance between Robert and each of the pivots is 2 m. Poppy and Quentin stand on the two remaining ends of the see-saws. Poppy weighs p kg and Quentin weighs q kg. The system is in equilibrium.
Show that, to the nearest whole number, p + q = 53 (8 marks)
0
reply
lolseriously?
Badges: 5
Rep:
?
#4
Report Thread starter 1 year ago
#4
(Original post by ghostwalker)
(a) 12g Nm

(b) 7F Nm

(c) F= 12g/7 N

You may need to evaluate those by putting in whatever appropriate value for g you're using.

If you get anything else, post working/thoughts.

Edit: I am assuming the see-saw remains horizontal.
Thank you! Turns out I was right after all!
0
reply
RogerOxon
Badges: 21
Rep:
?
#5
Report 1 year ago
#5
(Original post by lolseriously?)
These are the other questions I was trying to get my head around but also sorta stuck on! Please help!

(2).Alice, who weighs 50 kg, sits on the right-hand end of a light see-saw. Bob, who weighs 80 kg, stands on the opposite side at a distance x m from the end. The length of the see-saw is 4 m and it pivots about its centre.

a). Draw a diagram showing the forces acting on the see-saw due to the two people. Label the value of each force in newtons. (2 marks)
b). Write down the total clockwise moment about the centre in terms of x. ( mark)
c). Find the value of x for which the see-saw is in equilibrium. ( 2 marks)
d). Given that Bob remains on the opposite side to Alice, describe with inequalities the range of x for which the see-saw tilts towards Alice. (2 marks)
e).Describe one limitation of this model. (1 mark)
3). A 5000 kg bus hangs 12 m over the edge of a cliff and has 1000 kg of gold at the front. The gold sits on a wheeled cart. A group of n people, each weighing 70 kg, stands at the other end. The bus is 20 m long.
a).Write down the total clockwise moment about the cliff edge in terms of n. (7 marks)
b).Find the smallest number of people needed to stop the bus falling over the cliff. (2 marks)

c).One person needs to walk to the end of the bus to retrieve the gold. Find the smallest number of people needed to stop the bus falling over the cliff in this situation, including the one retrieving the gold. (4 marks)
4). Two identical 5 m light see-saws are joined at their ends. Robert, who weighs 80 kg, stands on top of the joint. The distance between Robert and each of the pivots is 2 m. Poppy and Quentin stand on the two remaining ends of the see-saws. Poppy weighs p kg and Quentin weighs q kg. The system is in equilibrium.
Show that, to the nearest whole number, p + q = 53 (8 marks)
We shouldn't be giving complete answers. Please post your working or exactly what you don't understand.
1
reply
lolseriously?
Badges: 5
Rep:
?
#6
Report Thread starter 1 year ago
#6
I am extremely sorry, I should have posted my working out with the questions, I was unaware that I had to do that. I will do very soon.
1
reply
RogerOxon
Badges: 21
Rep:
?
#7
Report 1 year ago
#7
(Original post by lolseriously?)
I am extremely sorry, I should have posted my working out with the questions, I was unaware that I had to do that. I will do very soon.
NP. This forum is about learning.
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

Current uni students - are you thinking of dropping out of university?

Yes, I'm seriously considering dropping out (57)
15.36%
I'm not sure (12)
3.23%
No, I'm going to stick it out for now (127)
34.23%
I have already dropped out (6)
1.62%
I'm not a current university student (169)
45.55%

Watched Threads

View All