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WAEC Physics 2020 Paper

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Question : 18

Total: 51

A 60 kg man stands on a weighing balance in an elevator. If the elevator accelerates upwards at

5 \text{ms}^{-2}

, determine the reading of the scale.

[ g = 10 \text{ms}^{-2}.

]

48.0°C
38.0°C
28.3°C
23.0°C

Solution:

GIVEN DATA:

where

\Delta L

is the increase in length

=0.01

L 1 is the initial length

=100

T_1 =20

T_2 =?

a is the linear expansivity of iron

=1.2 \times 10^{-5}\,{}^{\circ}\mathrm{C}

Formula

\Delta L = L_1 a \Delta T

\Delta T = \frac{\Delta L}{L_1 \alpha}

\Delta T

is the change in temperature

= T_2 - T_1

T_2 = \frac{\Delta L}{L_1 \alpha} + T_1

T_2 = \frac{0.01}{100 \times 1.2 \times 10^{-5}} + 20

T_2 = 8.3 + 20

T_2 = 28.3

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