question_answer

The mass of a brick is 2.5 kg. Its dimensions are \[10\text{ }cm\text{ }\times \text{ }5\text{ }cm\text{ }\times \text{ }2\text{ }cm\]. What will be its pressure exerted by it on the ground if it is resting on? (Take 1 kg wt = 10 N) (i) \[a\text{ }10\text{ }cm\text{ }\times \text{ }5\text{ }cm\text{ }base\] (ii)  \[a\text{ }5\text{ }cm\text{ }\times \text{ }2\text{ }cm\text{ }base\]

A)  5000 Pa, 25,000 Pa

B)  6000 Pa, 20,000 Pa

C)  4000 Pa, 15,000 Pa

D)  10000 Pa, 10,000 Pa

Correct Answer: A

Solution :

  (i) Force (F) = Weight of brick \[=2.5\text{ }kg\text{ }wt=2.5\times 10\text{ }N=25\text{ }N\] Area of base\[=10\times 5\text{ }c{{m}^{2}}=50\text{ }{{m}^{2}}=\frac{50}{10000}{{m}^{2}}\] \[\therefore \] \[Pressure=\frac{F}{A}=\frac{25}{50}\times 10,000\,Pa\]                                                 \[=5000\text{ }Pa\] (ii) Force = 25 N Area of base\[=5\times 2\text{ }c{{m}^{2}}=\frac{10}{10000}{{m}^{2}}\] \[\therefore \]\[P=\frac{F}{A}=\frac{25}{10}\times 10000Pa=25000\,Pa\] The correct answer is A.