State Secondary Certificate – ( SSC BOARD )

Recommended Question & Answers for Class 9

1. If x = 2 – α and y = 2 + α in a solution of 5x + 3y – 7 = 0 and x = 2β + 1 and y = β – 1 in a solution of 3x – 2y + 6 = 0 then find the value of α + β.

Given equation = 5x + 3y – 7 = 0
x = 2 – α and y = 2 + α
∴ 5(2 – α) + 3(2 + α) – 7 = 0
⇒ 10 – 5α+ 6 + 3α – 7 = 0
⇒ 9 – 2α = 0
⇒ 2α = 9 ⇒ α = 92 = 4.5

Given equation 3x – 2y + 6 = 0
x = 2β + 1 and y = β – 1
∴ 3(2β + 1)- 2(β – 1) + 6 = 0
⇒ 6β + 3 – 2β + 2 + 6 = 0
⇒ 4β + 11 = 0 ⇒ β = −114

∴ α + β = 92 – 114 = 18−114 = 74

2. Consider the following equation of motion and rewrite them for a free fall body v = u + at s = ut + ½ at²

For a free fall body u = 0; a = g and s

i) v = u + at ⇒ v = 0 + gt ⇒ v = gt
ii) s = ut + ½at² ⇒ h = 0 + ½gt² ⇒ h = ½gt²

3. On the basis of molecular weights of NaOH and H2O, which is heavier?

Molecular weight of NaOH = 23+16 + 1= 40
Molecular weight of H2O = (1 × 2)+ 16 = 2 + 16=18
Hence, NaOH is heavier than H2O.