Science questions in short. [3 marks ]

We make use of muscular force to hold a bucket of water above the ground. This muscular force acts against the force of gravity that pulls the bucket towards the ground. The two forces are equal in magnitude but opposite in direction. Therefore, the net force on the bucket is zero. Hence, there is no change in its state of motion.

Air pressure is involved in rubber sucker. When we stick the rubber sucker to a surface, most of the air between the rubber and the surface escape thus the atmospheric pressure acts on it. To remove the rubber sucker, we have to apply a force equal to the atmospheric pressure.

Because the atmosphere also pressurize the body. Diving down 100 meters will pressurize the gasses in the body and they will compress, like the air in our lungs and if the lung volume gets below half a litre the lungs can get partly filled with blood plasma. But sorry no bone crushing. But if you take a big breath and hold it while you ascend from 100 meters to the surface, your ribs may start to break.

A dam is thicker at the bottom than at the top because the forces exerted are strongest close to the ground. Water pressure increases proportionally with depth, so the lower portion of the dam has greater water pressure exerted upon it. The increasing thickness of the lower dam also helps it support its own weight.

As we know that pressure exerted by the body is inversely proportional to the area where force is applied. So, the thinner rod, i.e. rod B will sink more because it has less area of cross-section in contact with the surface, hence it will exert more pressure on the sand with respect to the rod A.

Crushing can experiment. When a can filled with hot water is closed and is cooled down rapidly by pouring cold water on it, it will crush instantly. This experiment proves that there is a huge atmospheric pressure exerts on everything on the surface of the earth.

Because needle tip has very less area of cross-section in comparison to that of our finger and we know that pressure exerted by a force is inversely proportional to the area where it has been applied, so pressure exerted will be more by the needle tip than the finger.

Magnetic force is acted upon a body by the magnetic lines of force. These are imaginary closed line of lines of force which emanate from the N pole f the magnet and goes into the S pole of the magnet. So, a magnet can influence a magnetic material like a piece of iron even when they are not in contact thus magnetic force is a non contact force.

The weight of the tank (its mass being acted upon by the force of gravity) is spread over a larger surface area (the big steel belt), giving it a smaller pressure and therefore it makes it sink in less, allowing it to travel faster over more surfaces where others would with less surface area.

While walking on a sandy surface, one needs the footwears of larger area so that the pressure exerted on the ground is minimum. So, in this case, the woman having the sandals with pointed heels will be less comfortable in walking while the other woman wears sandals with flat soles feels more comfortable while walking on sandy beach.

The round piece of cloth on their heads increases the area on which the force (weight of the load) will act. We know that, the pressure is inversely proportional to area. Therefore, increase in area reduces the pressure and this helps the porter to carry the heavy load easily.

If the magnitudes of the two forces acting in opposite direction on an object are equal then the object will not move at all. On the other hand, if the magnitudes of the two forces are unequal then the net force acting on the object is the difference between the two forces and the object will moves towards the direction of the larger force applied.

Yes, it is compulsory that non-contact forces are having both the properties, i.e., attraction and repulsion as both these properties depend on the charge or pole of the object. The object having positive charge will attract a negatively charged object and the same object with positive charge will repel another positively charged object. Thus both attraction and repulsion are there in the same object.

The archer shoots an arrow by applying muscular force to stretches the string of the bow. When the string is released, it regains its original position that provides the initial force to set the arrow in motion horizontally.
The force of gravity that acts on the arrow in the downward direction and hence, the arrow ultimately falls to the ground.

The force exerted by the muscles of arms or legs or any other body part in order to do some work is called muscular force. Kicking a football, pushing a car are some examples. Mechanical force is a force between two objects which require physical contact with each other. It is the force created by the movement of an object over a distance. It requires a medium to travel. Force used by tractor or bulldozers, pushing a door are some examples.

It means for force to come into play, atleast two object must interact with each other. For example: If the man pushes the car with his hands due to which the car starts moving, there is an interaction between man and a car. During this interaction force arises which Acts on the car and makes it move in the direction of applied force.

Force of gravity or gravitational force is the force with which the earth attracts the objects towards it. This force ensures every object gets attracted towards the earth’s surface. For example: when a ball is thrown upwards, after reaching a certain height is starts to fall down. Sir Isaac Newton introduced the gravitational force.