Ans. The state of motion of an object is described by its speed and the direction of motion. The state of rest is considered to be the state of zero speed. An object may be at rest or in motion; both are its states of motion.
Ans. The cutting edges of tools like blades, knives etc., are provided with sharp edges to cut the things easily because the smaller the area, larger the pressure on a surface for the same force.
Ans. The tip of the sewing needle is sharp so that due to its sharp tip, the needle may put the force on a very small area of the cloth, producing a large pressure sufficient to pierce the cloth being stitched.
Ans. The force of gravity causes all the objects to fall towards the earth. Thus, when a ball is dropped from a height, its speed increases gradually because of the force of gravity acting on it.
Ans. By this they increase the area of contact of the load with their head. So, the pressure on their head is reduced and they find it easier to carry the load.
Ans. Shoulder bags are provided with broad straps and not thin strap so that the weight of the bag may fall over a large area of the shoulder of the child producing less pressure on the shoulder.
Ans. Magnetic force is involved in this process. The magnetic force acts even from a distance. The magnet exerts a magnetic force on objects made of iron, steel, nickel and cobalt.
Ans. In cricket, a batsman plays his or her shot by applying a force on the ball with the bat. In this example the speed and the direction of the moving ball change due to the application of a force.
Ans. The force of friction always acts on all the moving objects and its direction is always opposite to the direction of motion. Since the force of friction arises due to contact between surfaces, it is an example of a contact force.
Ans. If there is no movement on either side, the force applied from both side is equal in magnitude.
Ans. The walls of a dam are much thicker at the bottom than it is at the top. This is because the pressure of the water is much greater deeper down and the dam needs to be thick at the bottom so that it is strong enough to withstand this larger pressure.
Ans. The examples of non-contact forces are:
i. Magnetic force
ii. Electrostatic force
iii. Gravitational force
Ans. The two forces acting on the rocket are the force of gravity, which pulls the rocket towards the ground, and the force of friction due to earth's atmosphere, which opposes its motion.
Ans. Every object in the universe, whether small or large, exerts a force on every other object. This force is known as the gravitational force. Example: Water begins to flow towards the ground as soon as we open a tap.
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