M2 Tricky Questions

Hi, I have OCR M2 exam on friday and am wanting to clear somethings up, any help will be greatly appricated.

1) A rigid body ABC consists of two uniform rods AB and BC, rigidly joined at B. The lengths of AB and BC are 13cms and 20cms respectably, and their weights are 13N and 20N respectively. The distance of B from AC is 12cms. The body hands in equilibrium, with AC horizontal, from two vertical strings attached at A and C. Find the tension in each string?

2) A ball of mass 0.08kg is attached by two strings to a fixed vertical post. The strings have lengths 2.5m and 2.4. The ball moves in a horizontal circle, of radius 2.4m, with a constant speed of V m/s. Each string is taut and the lower string is horizontal. The modelling assumptions made are that both strings are light and inextendable, and that there is no air resistance find:

i) The tensin in each string when v = 10.5

ii) The least value of V for which the lower string is taunt.

Many Thanks

Streety

Just spotted the method for Q1:

The sketch is key:

Draw the triangle as it will hang - AC along the x-axis (I don't think it matters whether you put B above or below AC)

length of AC is 21. Dropping a perp from B lands at x=5, call this point on AC D

You have 2 triangles ABD is 5 13 12 and BDC is 12 16 20

You have T1 upwards at A (0,0) T2 upwards at C (21,0)

CoM of each rod acts at mid-point, so down at (2.5,0) and (13,0)
Take moments about (0,0) and (21,0) (and/or resolve vertically)

Nasty if you draw the sketch otherwise!

I'd better work it out now!

Aitch

Just spotted the method for Q1:

The sketch is key:

Draw the triangle as it will hang - AC along the x-axis (I don't think it matters whether you put B above or below AC)

length of AC is 21. Dropping a perp from B lands at x=5, call this point on AC D

You have 2 triangles ABD is 5 13 12 and BDC is 12 16 20

You have T1 upwards at A (0,0) T2 upwards at C (21,0)

CoM of each rod acts at mid-point, so down at (2.5,0) and (13,0)
Take moments about (0,0) and (21,0) (and/or resolve vertically)

Nasty if you draw the sketch otherwise!

I'd better work it out now!

Aitch

Hi, I have OCR M2 exam on friday and am wanting to clear somethings up, any help will be greatly appricated.

1) A rigid body ABC consists of two uniform rods AB and BC, rigidly joined at B. The lengths of AB and BC are 13cms and 20cms respectably, and their weights are 13N and 20N respectively. The distance of B from AC is 12cms. The body hands in equilibrium, with AC horizontal, from two vertical strings attached at A and C. Find the tension in each string?

2) A ball of mass 0.08kg is attached by two strings to a fixed vertical post. The strings have lengths 2.5m and 2.4. The ball moves in a horizontal circle, of radius 2.4m, with a constant speed of V m/s. Each string is taut and the lower string is horizontal. The modelling assumptions made are that both strings are light and inextendable, and that there is no air resistance find:

i) The tensin in each string when v = 10.5

ii) The least value of V for which the lower string is taunt.

Many Thanks

Streety

erm......i got dodgy answers lol streetyfab do u hav the answers???

for BA i got t=138N

BC i got t=326 2/3N

they don't look right lol

Hi, I have OCR M2 exam on friday and am wanting to clear somethings up, any help will be greatly appricated.

1) A rigid body ABC consists of two uniform rods AB and BC, rigidly joined at B. The lengths of AB and BC are 13cms and 20cms respectably, and their weights are 13N and 20N respectively. The distance of B from AC is 12cms. The body hands in equilibrium, with AC horizontal, from two vertical strings attached at A and C. Find the tension in each string?

2) A ball of mass 0.08kg is attached by two strings to a fixed vertical post. The strings have lengths 2.5m and 2.4. The ball moves in a horizontal circle, of radius 2.4m, with a constant speed of V m/s. Each string is taut and the lower string is horizontal. The modelling assumptions made are that both strings are light and inextendable, and that there is no air resistance find:

i) The tensin in each string when v = 10.5

ii) The least value of V for which the lower string is taunt.

Many Thanks

Streety

Hi, I have OCR M2 exam on friday and am wanting to clear somethings up, any help will be greatly appricated.

1) A rigid body ABC consists of two uniform rods AB and BC, rigidly joined at B. The lengths of AB and BC are 13cms and 20cms respectably, and their weights are 13N and 20N respectively. The distance of B from AC is 12cms. The body hands in equilibrium, with AC horizontal, from two vertical strings attached at A and C. Find the tension in each string?

2) A ball of mass 0.08kg is attached by two strings to a fixed vertical post. The strings have lengths 2.5m and 2.4. The ball moves in a horizontal circle, of radius 2.4m, with a constant speed of V m/s. Each string is taut and the lower string is horizontal. The modelling assumptions made are that both strings are light and inextendable, and that there is no air resistance find:

i) The tensin in each string when v = 10.5

ii) The least value of V for which the lower string is taunt.

Many Thanks

Streety