Tiêu đề TOPIC 3 FORCE - WazaElimu.com.pdf ✅

23 PROPERTIES OF GRAVITATIONAL FORCE  It is always attractive.  It is a weakest force among the four basic forces.  It operates over a very long distance.  It is a centre force.  Pull the objects towards the centre of the earth. b) ELECTROMAGNETIC FORCE.  This is the force which causes magnetic and electrical effect. Some example where electromagnetic force is involved include:-  In formation of molecule of a substance. Atoms attract each other to form molecules. This is due do electromagnetic forces.  In two parallel wires carrying current. If placed each other, electromagnetic force acts on the wires. PROPERTIES OF ELECTROMAGNETIC FORCE  It may be attractive or repulsive in nature.  It is a central force  It is stronger than gravitational force.  Operate over a very long distance. c) STRONG NUCLEAR FORCE (STRONG FORCE).  This force holds the nucleus of an atom together (neutron and proton).  This force occurs in the fusion and fission of the nucleus of the atom. PROPERTIES OF STRONG FORCE 1. It is basically an attractive force. 2. It is a short-range force (distance) of about 10-14 m 3. It is a non-central force. 4. It is stronger that gravitational force. d) WEAK NUCLEAR FORCE (WEAK FORCE).  This is the force responsible for various trends of radioactive decay.  The decay fundamental particles such as beta particles. PROPERTIES OF WEAK FORCE  It is much stronger than the gravitational force but weaker than the strong nuclear and electromagnetic forces.  It acts on small range (distance) of up to 10-17 m. EFFECTS OF FORCES 1. Stretching force 2. Compression force and restoring force 3. Attractive force 4. Repulsive force 5. Torsional force 6. Frictional force 7. Viscosity 8. Air resistance 9. Normal force 10. Applied force
24 1. STRETCHING FORCE  This is the force that is passed through a string, cable or wire when it is pulled tight by forces acting on it from both ends.  It is a force used in lifting or pulling heavy loads. So, if an object hangs from a rope, the gravitational force point downward while the tension force on the rope points upwards. 2. COMPRESSIONAL FORCE AND RESTORING FORCE Compressional force  This is the force which when applied to an object results in a decrease in its volume. Restoring force  This is the force which causes an object to return to its original shape and size. For example: When a spring is compressed, its length is reduced. However the restoring force will help it to regain its original shape and size. 3. ATTRACTIVE FORCE  This is the force by which an object attracts another object. Example: A magnet exerts an attractive force on a piece of metal made of iron. 4. REPULSIVE FORCE  This is the force of separation that an object exerts on another object. Example: like pole of magnets or like charges exerts a repulsive force when brought near each other. 5. TORSIONAL FORCE  This is a force when applied on an object, the object does not return to its original shape and size.  A torsion force causes the twisting of an elastic material. 6. FRICTIONAL FORCE This is the force which opposes the motion of an object. The friction force is divided into two types such as kinetic (dynamic) friction and static friction. 7. VISCOSITY  This is the force which resists a flow of the fluids. For example: Water has low viscous force than cooking oil. Also honey has a higher viscosity than cooking oil. 8. AIR RESISTANCE  This is the force that resists the movement of an object through the air.  Air resistance is an example of fluid resistance (fluid force). Fluid resistance: This is the force exerted on an object moving through a fluid ( gas or liquid). Air resistance (fluid resistance) depends on: i) The size and shape of an object. ii) The speed of an object through the fluid. iii) The density of the fluid.