Science Que-Ans (Each of 2 Mark )

Camels have large flat feet so that there is a greater area in contact with the sand which produces less pressure on the sand and the camels can move easily on the sand.

The mass of a stone is very small, due to which the gravitational force produces a large acceleration in it. Due to large acceleration of stone, we see stone falling towards the earth. The mass of earth is, however, very, very large. Due to the very large mass of the earth, the same gravitational force produces very, very small acceleration in the earth, that it cannot be observed. And hence we do not see the earth rising up towards the stone.

The foundations of buildings and dams are laid on a large area of ground so that the weight of the building or dam produces less pressure on the ground and they may not sink into the ground.

The truck and motorbus have wider tyres with respect to the property that "more the area, less the pressure." As the area is more the pressure will decrease, so there will be less need for applying more pressure to handle the vehicle. The vehicle will move smoothly.

If the buoyant force exerted by the liquid is less than the weight of the object, the object will sink in the liquid. If the buoyant force exerted by the liquid is equal to or greater than the weight of the object, the object will float in the liquid.

When objects are placed in water, their mass does not change. They seem to feel lighter, though because of buoyancy. Archemedes's principle states that the force pushing on an object under water is equal to the mass of the water it has pushed out of the way.

Newton's law of universal gravitation states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Big boulders weigh much less while in water and as such are easily moved by the flood.

The block of the wood can be float on the water and it can be similar in size block of the concrete and it can be used as the anchor. Because the block can be light weighted on the other hand and it can be sized in similar so the concrete is heavy this is the reason for using the anchor.

To avoid sinking their foundations are made wide, so that pressure on the ground decreases. Buildings are massive structures which exerts tremendous pressure on the ground and likely to sink.

When a lot of salt is dissolved in water, then the density of salt solution becomes much more than pure water. Due to its much higher density, the salt solution exerts a greater upward buoyant force on the egg making it rise and then float.

A force of one newton spread over a square meter doesn't produce much pressure, as it turns out. A pascal unit is equal to about a hundredth of a millibar, and that's pretty low, considering that atmospheric pressure is approximately equal to 1 bar.

The floating or sinking of a body in the water is decided by the density of both the body and water’s buoyant force acting on the body by the liquid. The density of plastic is less than the water and the buoyant force exerted by water on the plastiq block is greater than the force exerted by plastic on the water.

As more and more volume of the solid object is immersed in the liquid, the upward ‘buoyant force’ also keeps on increasing. When the object is completely immersed in the liquid, the buoyant force acting on the solid becomes maximum and remains constant thereafter.

The actual shape of the orbit of a planet around the sun is elliptical. The assumption made by the Newton regarding the shape of an orbit of a planet around the sun was that the orbit of a planet around the sun is ‘circular’.

Archimedes' Principle: When an object is wholly (or partially) immersed in a liquid, it experiences a buoyant force (or upthrust) which is equal to the weight of liquid displaced by the object. Buoyant force on an object = weight of liquid displaced by that object.

The body will sink less in water. This is because the density of water is more than that of kerosene due to which water will exert a greater upward buoyant force on the body.

1. The boat sinks a little more in water, that is, the boat floats lower in water.
2. The weight of water displaced (by the submerged part of the boat) increases.
3. The buoyant force acting on the boat increases.

The Earth and the moon experience equal gravitational forces from each other. However, the mass of the Earth is much larger than the mass of the moon. Hence, it accelerates at a rate lesser than the acceleration rate of the moon towards the Earth. For this reason, the Earth does not move towards the moon.

All objects fall on ground with constant acceleration, called acceleration due to gravity (in the absence of air resistances). It is constant and does not depend upon the mass of an object. Hence, heavy objects do not fall faster than light objects.

1. The reading of spring balance will not change if a cork is placed in water because cork, being lighter than water, floats in water.
2. The reading of spring balance will change if a piece of heavy metal is placed in water because heavy metal being denser than water, sinks in water.

A person in water feels an upward force called buoyant force, exerted by the water acting in upward direction. This reduces the weight of the body and hence, we feel lighter in a swimming pool.

The two equal weights of unequal volumes which are balanced in air, will get imbalanced when they are completely dipped in water because due to their unequal volumes, they will displace unequal volumes of water and hence suffer unequal loss in weight.

According to the universal law of gravitation, two objects attract each other with equal force, but in opposite directions. The Earth attracts the moon with an equal force with which the moon attracts the earth.

The buoyant force or upthrust depends upon two factors: Volume of the object immersed: If the volume of the object is more, the buoyant force acting on it is more and if the volume of the object is less, then the buoyant force acting on it is less.

A piece of glass sinks in water but it floats in mercury because density of glass is more than that of water but less than that of mercury.

The moon will begin to move in a straight line in the direction in which it was moving at that instant because the circular motion of moon is due to the centripetal force provided by the gravitational force of earth and if gravitational force becomes zero it means no centripetal force is there to help the moon to move in circular orbit. Therefore it will move in a straight line.

Perihelion and Aphelion, The perihelion is the point on the orbit of a planet or comet that is closest to the sun. The point on the orbit farthest from the sun is the aphelion. The speed of a body in the solar system is greatest at the perihelion and least at the aphelion.

The reading on spring balance will be zero. This is because the weight of floating block of wood is fully supported by the liquid in which it is floating and hence it does not exert any force on the spring balance.

1. Universal law of gravitation is used to determine the masses of the sun, the earth and the moon accurately.
2. Universal law of gravitation helps in discovering new stars and planets.