physic forces

• a force is a push or a pull
• we cannot see forces, we can feel or see effects of forces.
• example of forces are during collision of two cars, we can cleary see damage caused by impact.
• forces can easily change the shape and size of elastic objects such as elastic band and tyre.
• forces can also stop a moving object or start the motion of stationery object. forces can also accelerate or decelerate moving objects.
• friction is the force that tries to prevent materials sliding across each other. friction tends to slow motion
• friction is an essential force required for walking, climbing, holding objects, slowing down vehicles and even for wearing our underpants
• however, it can also be an annoyance since it slow down objects, it causes the wear and tear of surfaces and it may produce unwanted heat
• using lubricants such as oil or grease
• there are two main types forces namely: contact forces and non contact forces.
• contact forces occur when one body touches another body. they include tension, compression, friction and normal reaction.
• example of contact force are frictional forces, tensions and forces exerted during collisions.
• non contact forces include gravitational forces, magnetic forces and electrical forces
• weight are measured in Newton(N) using a Newton meter or force meter or a spring balance
• the mass of an object is the amount of matter it contains.
• mass is measured in kilogram(kg)using a beam balance or a sliding mass balance.
• the weight of an object is the force of gravity acting on a object
• weight is measured in Newton(N)using a spring balance.
• When a bar magnet is suspended horizontally by using a paper stirrup
• the magnet oscillates until it comes to rest aligned in a north south direction.
• the pole of the magnet pointing in the northern direction is called the north pole and the other end of the magnet called the south
• magnets come in different shapes namely: bar magnets, U-shaped magnets, horseshoe magnets
• the like poles of a magnet repel and unlike poles attract
• astronauts would feel light on Mars as the force of gravity on Mars is weaker than the force on Earth
• Camels and elephants have large flat feet spread their weight over a large area
• the camel does not sink into the desert sand and the elephant does not sink into soft ground as these animals exert a relatively small pressure on the ground
• the studs have a small surface area in contact in the ground
• hence, the football players will exert a sufficiently high pressure on the ground, giving them a good grip while running
• high pressure are needed force cutting vegetables and meat with a sharp knife
• air exerts a pressure also known as atmospheric pressure.
• the air pressure decreases as we go up mountains such a Mount Everest.
• it is difficult to push an object on a rough surface because there is a lot of friction that tends to slow down the motion of the object
• it is easier to push the same object across a smooth surface, as there will be less resistance to motion.