**Numericals Based on Class 9 Science Thrust and Pressure**

Q.1. A force of 100 N is applied on an object of area 2 m^{2}. Calculate the pressure.

Q.2. The force on a phonogram needle is 1.2 N. The point has a circular cross-section of radius 0.1mm. What pressure does it exert on the record in (i) Pa (ii) atm ?

Q.3. A nail is driven into a wooden board by using a hammer. The impact of the hammer on the head of nail produces a thrust of 25 N. If the area of the head is 0.5 mm^{2} and of the tip 0.1 mm^{2}, find the pressure on the head and the tip of the nail.

Q.4. A force of 15 N is uniformly distributed over an area of 150 m^{2}. Find the pressure in pascals.

Q.5. A block of wood is kept on a table top. The mass of the wooden block is 5 kg and its dimension are 40 cm x 20 cm x 10 cm. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table with its sides of dimensions (a) 20 cm x 10 cm (b) 40 cm x 20 cm. Given g = 9.8 m/s^{2}.

Q.6. How much force should be applied on an area of 1 cm^{2} to get a pressure of 15 Pa?

Q.7. A block weighing 1.0 kg is in the shape of a cube of length 10 cm. It is kept on a horizontal table. Find the pressure on the portion of the table where the block is kept.

Q.8. Find the thrust acting on the human body due to atmospheric pressure. Take the surface area of a man of middle size to be 1.5 m^{2} and atmospheric pressure (1 atm) = 1.013 x 10^{5} Pa.

Q.9. A boy weighing 60 kg f is wearing shoes with heel area of cross section 20 cm^{2} while a girl weighing 45 kg f is wearing shoes with heel of area of cross section 1.5 cm^{2}. Compare the pressure exerted on ground by their heels when they stand on the heel of one floor.

Q.10. A cube of edge length 10 cm is placed inside a liquid. The pressure at the centre of the face is 15 Pa. Find the force exerted by the liquid on this face.

Q.11. A force of 16 N is distributed uniformly on one surface of a cube of edge 8 cm. Find the pressure on this surface.

Q.12. A car weighs 1200 kg. This weight is evenly distributed on 4 wheels. If the pressure in each tyre is 15 kg wf/cm^{2}, what is the area of each tyre in contact.

Q.13. Calculate the greatest and the least pressure exerted by a metal block of size 20 cm x 8 cm

x 5 cm and having a mass of 5 kg.

Q.14. A hydraulic automobile lift is designed to lift cars with a maximum mass of 3000 kg. The area of the piston carrying the load is 425 cm^{2}. What maximum pressure would the smaller piston have to bear?

Q.15. The pressure due to atmosphere is 1.013 x 10^{5} Pa. Find the force exerted by the atmosphere on the top surface of a table 2.0 m long and 1.0 m wide.