Types of Forces (For Unit 1) PDF

TYPES OF FORCES (FOR UNIT 1) Forward force/Thrust: This is the force that causes a body to move forward. Examples include force from engine in a car, propellers of a ship, jet engines of aircrafts, etc Tension: Tension causes/tends to pull a body (such as a string or a rope) apart. Tension can onl...

TYPES OF FORCES (FOR UNIT 1) Forward force/Thrust: This is the force that causes a body to move forward. Examples include force from engine in a car, propellers of a ship, jet engines of aircrafts, etc Tension: Tension causes/tends to pull a body (such as a string or a rope) apart. Tension can only act on a body when the string/rope is taut. *Tension in a string / rope acts in both directions ILLUSTRARION Friction: Friction is the opposing force which acts in the opposite direction to the motion of a body. Friction is a contact force and acts only when the bodies are in contact with each other. Friction doesn’t only oppose motion. It can also cause a body to move. *Friction between two surfaces always has a maximum value. This is illustrated in the diagram below When the truck moves forward, the box stays on top of it until the truck does not exceed a certain acceleration because frictional force between the truck and the block is what causes the block to accelerate. If the acceleration of the truck exceed a certain value, the friction will not be able to provide the resultant force needed to cause that acceleration. When the tyre rolls, it pushes on the road backward. According to third law, the road pushes on the tyre forward causing it to move forward. This push is contact force between the tyre and road – Friction If the road was slippery, the tyres would roll because of the thrust from the engine, but the car would not move forward because the friction is not enough to move the car forward. The same concept applies to YOU when you’re walking. Imagine trying to walk on a very slippery surface. Air resistance: Air resistance is a resistive force that acts in the opposite direction to the motion of a body. This is a contact force and arises due to the contact between the surface of the body and air particles. Air resistance depends on two factors – Speed and surface area. Drag Force: It is the opposite force that acts on a body when it is moving through a fluid such a water, oil or any other viscous material. This will be discussed in details in the topic - FLUID MECHANICS Upthrust: Upthrust is the upward force that acts on a body when it’s immersed in a fluid. Upthrust is also referred to as buoyant force. Normal contact/reaction force : It is the force that acts on a body perpendicular to the surface. Normal reaction force is the 3rd law pair force of the push of a body on the surface but NEVER the third law pair force for weight. Normal reaction force gives a person the feeling of their weight. When a person falls freely, the only force acting on the person is the weight. Since there is no normal reaction force, the person feels weightless. This is called apparent weightlessness because even though the person has a weight, he “feels” weightless. JUMPING While jumping a person exerts an extra push on the ground by bending their knees. The total push on the ground from the man is greater than his weight. According to Newton’s 3rd law, the ground exerts a reaction force on the man greater than his weight. There is an unbalanced force on the man upward causing him to accelerate upward (while his feet are in contact with the ground)