ACTIVITY No.
2
LAW OF MOMENTS
Aim: To determine the mass of a given body using a meter scale by principle ofFmoments.
Apparatus: Ameter scale suspended at C.G., hanger with slotted weights, a body of unknown
mass.
Diagram:
meter scale
C.G
m. m,
Fig. Experiment Setup
Formula:
m, r =m, I,
m, =I ,
Procedure:
1. Balance the meter scale carefully at its C.G. and note down the position of the C.G.
2. Suspend the body of unknown mass (m, ) at a fixed distance (r,)from C.G. as shown in the
figure.
3. Suspend the hanger with slotted masses (m,)at some distance from C.G. to the other side as
shown in the figure.
4. Adjust the distance (r,)in such a way that, the meter scale becomes horizontal.
5. Repeat the steps 3 and 4 by changing the slotted weights (m, ) and note down the corresponding
distance (r,)ineach case for three times.
Qbservations :
Fixed distance of unknown mas from C.G, =r, cm.
Sr. Mass suspended Distance of hanger from m, r, gem Unknown (m)
No. with hanger (m,)g C.G. at balance (r,)em mass g
20 17 340
2 30 27
3 19 760
Mean mass
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Result: The unknown mass of abody (m)
Arrcaution: Find centre of gravity of scqle using knife edge.
FOR NOTES
Remark and sign of teacher:
75
Activity NO. 3
ROLLING FRICTION
Aim: To detemine the force of limiting friction for rolling of aroller on a horizontal plane.
Apparatus: Awheel base wooden/metal block(or trolley), weight box, friction less pulley,
a thread.
a plane horizontal plane, a balance a pan and
Theory: Rolling friction is that fone of friction which comes into play when a body is
the surtace of another body. rol ing on
Magnitude of the rolling friction is proportional to the normal reaction
EaN
F.-4N
F
W
Where =Coeficient of rolling friction
F- Magnitude of force of rolling friction
N= Normal reaction.
Diagram :
Fig. Experiment Setup
Procedure :
1. Measure the weight of wooden roller block (W) by using balance.
2. Measure the weight of Pan (P,) by using balance,
3. Place wooden roller block on the horizontal plane plank. The one end of thread to block and
other to the pan by passing it over the pulley. Pan should be freely suspended in air and threa
between pulley and block should be horizontal.
4.. Add weights in the plan gradually till the roller just starts rolling.
5. Note that minimum weight in the pan for which roller just start rolling.
6. Repeat th¹ experiment by putting weights in the step of 50g on the wooden block.
7., In each case find the force of limiting friction (F)
Observations :
1. Weight of empty wooden block roller (W) =...22...g.
2. Weight of emptyscale pan (P) =........g..g.
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pbserationTable.
Sr. Masson Total load Mass in the
W= (WotW)
Total Effort F Mean
No.theblock pan P, g.wt Fr=(PotPi)
g.wt W
Wig.wt g.wt
28
20 29
2
133 30 34 o212
01222D22|6
3
4
fo
52O 0392
Calculation:
Result :
1. Coeficient of rolling friction for the given surface , F..9:86
2. As the weight of pulley increases the effort increases.
Precautions :
1. Table top should be horizontal.
2. Pulley should be frictionless.
small steps.
3. Weight in the pan should be increased in
4. Table top should be top gently. FOR NOTES
Remark and sign of teacher:
77
