Forces Flashcards
What is a force?
A force is any push or pull on an object. It is a vector quantity.
What is a resultant force?
The total force acting on an object in a certain direction.
How do you calculate resultant force when forces are in the same direction?
Add them and keep the same direction.
How do you calculate resultant force when forces are in opposite directions?
Subtract the smaller force from the larger one and keep the direction of the larger force.
How do you calculate resultant force when forces are perpendicular?
Use the Pythagorean theorem:
๐น = Sqrt(๐น(1)^2 +๐น(2)^2)
How do you find the resultant force when forces act at an angle?
- If they have the same starting point โ Use the Parallelogram Method.
- If they follow each other โ Use the Triangle Method.
What is gravity?
The force that pulls objects toward Earth.
What is the formula for weight?
w = m ร g
where:
- ๐ค = weight
- ๐ = mass (kg)
- ๐ = acceleration due to gravity (9.8 ๐/๐ ยฒ, use 10 ๐/๐ ยฒ in exams).
What is friction?
A force that opposes motion between solid surfaces.
What is air resistance?
A force that opposes motion in air. It increases with speed or larger surface area.
What is upthrust?
An upward force that occurs in liquids and gases.
What is tension?
A force that acts in strings, wires, and cables (e.g., a ceiling fan hanging from a wire).
What is normal force?
A contact force exerted by a solid surface perpendicular to an object.
What is Newtonโs First Law of Motion?
If the resultant force is 0, an object remains at rest or moves at constant velocity.
What is Newtonโs Second Law of Motion?
The resultant force acting on an object is equal to mass ร acceleration:
- ๐น = ๐ x ๐
What is the relationship between force, mass, and acceleration?
- Force (F) is directly proportional to mass (m).
- Force (F) is directly proportional to acceleration (a).
- Mass (m) is inversely proportional to acceleration (a).
What is Newtonโs Third Law of Motion?
For every action, there is an equal and opposite reaction.
What happens immediately after a skydiver jumps?
He falls under the effect of his weight only โ Acceleration is constant, speed increases.
What happens as the skydiver falls at the start?
His speed increases, so air resistance increases โ Acceleration and resultant force decrease.
* Resultantforce = weight โ airresistance
What happens when the skydiver reaches terminal velocity?
Air resistance = weight โ Resultant force = 0 โ Speed becomes constant. (Newtonโs Second Law)
What happens when the parachute opens?
Surface area increases, so air resistance > weight โ The skydiver decelerates.
- Resultantforce = airresistance โ weight
What happens when the skydiver reaches terminal velocity again?
His speed decreases, so air resistance decreases until it equals weight โ He falls at a safe constant speed.
What is circular motion?
Motion where an object moves at constant speed but is always accelerating because its direction changes.
What is the force that keeps an object moving in a circle?
Centripetal force.
In which direction does centripetal force act?
Toward the center of the circular path.
What causes circular motion?
Friction between the object and the surface (e.g., car tires on a road).
What is a freeโbody diagram and why is it useful in analysing forces?
A freeโbody diagram is a simplified drawing that shows all the forces acting on an object. It helps visualize forces, resolve them into components, and set up equilibrium equations.
