If the two forces are acting in the same direction, the resultant is the sum of both forces, in the same direction. The magnitude of resultant force in the following figure is 5N, which is acting to the right.
If the two forces are acting in the opposite directions, the resultant force is the difference of two forces which acts in the direction of the larger force. The magnitude of resultant force in the following figure is 1N, which is acting to the right.
In the following figure, resultant force is acting to the left. The magnitude of resultant force in the following figure is 3N, which is acting to the left.
Force of Friction
The force which opposes the motion of a moving body is called friction.
When a body slides over the surface of another body, an opposing force, which is known as force of friction is set up between two touching, surfaces to resist the motion.
Force of friction tends to decelerate a body and always acts in the opposite direction of motion. Surfaces which look very smooth also cause force of friction. Brakes are applied to stop moving vehicles by using force of friction. It converts the kinetic energy into heat and sound energies.
In the following figure, force of friction due to surface of the ground is 10 N. Resultant force of 40 N is acting to the right.
Reducing Friction
- Friction can be reduced by lubrication to separate the surfaces in contact.
- It can be reduced by streamlining.
- Friction can be minimizing by polishing surfaces.
Advantages of Friction
Friction is not always a BAD thing.- Without friction between our shoes and the ground we would not be able to walk.
- Friction is needed to make knots work.
- Friction enables the brakes of cars to work.
- Friction is also used in the clutch of a car.
- Without friction the wheels of a car would just spin and the car would not be able to go around a corner.
- Air Friction slows down the parachute.
Friction with the Road
The friction between the wheels of a car and the road produce a sideways force which enable the car to change its velocity.
This change in velocity is a change in direction. The car goes around the corner.
The Parachute
Air resistance increases with the speed of an object.
When the air resistance equals the weight the parachutist will not fall any faster.
