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YSA
Model Paper
Subject:
Physics
Class: IX
Answer
Key
Section – C
Q.3 a) From book page no. 18. under the
headings of random error and
systematic error.
b)
Final velocity,
vf = 0ms-1
Height,
h = 1.8m.
Acceleration
due to gravity, g = 10ms-2
Initial Velocity, Vi = ?
Sol.
2aS = vf2 – vi2
2gs = vf2 – vi2
2(-10ms-2) (1.8m) = (0)2 (vi)2
36m2S-2 = - vi2
Taking
square root on both sides.
Vi = 6mS-1
Q.4 a) Book Page No. 47, under the heading
motion of bodies by string.
Case – I
b)
Distance towards North = 800m
-
--
--
West =
1300m
-
--
-- in 3rd direction = R = ?
From
fig.
R2 = (OA)2 + (OB)2
= (800)2 + (1300)2
= 640000 + 1690000
= 2330000
R = 1526.4m.
Distance
covered in 3rd direction is 152.6 m.
Q.5 a) Weight of Painter, W1 = 700N.
---
--- -- --Platform,
W2 = 200N.
Let
T1 and T2 are tensions in the strings
According
to first condition of equilibrium.
Up ward force = Down ward force
T1 + T2 = W1 + W2
T1 + T2 = 700N + 200N
T1 + T2 = 900N
Calculating
torques at Pt. D.
Clockwise
torque = Anti clockwise torque
T1
* CD
=
W1 * AD + W2 * BD
T1
* 3m
=
700N * 2m + 200N * 1.5m.
3T1m
=
1400Nm + 300Nm
3T1m
=
1700Nm
T1
=
T1
=
566.66
=
566.67N
As
T1 + T2 =
900N
T2 =
900 – 566.7
=
333.3N
Q.5 b) Page No. 92, heading 7.8 from 2nd
paragraph to end of topic.
Q.6 a) Page No. 149. Definition under the
heading of conduction, convection
and
radiation of Pascal’s law
and hydraulic Press.
b)
Page No. 127 of the text book.
c) Unlike other materials the behaviour of water is
unusual. By increasing or decreasing the temperature
of ∆ C0 , the water expands this
unusual behaviour is called anomalous expansion of
water.
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