Forces Flashcards
(18 cards)
What is the definition of a force?
A force is a push or pull on an object that is caused by it interacting with something. It is a vector quantity, measured in newtons (N).
What are the two main types of forces? Give examples.
- Contact forces – friction, air resistance, tension, normal contact force.
- Non-contact forces – gravitational force, magnetic force, electrostatic force.
State Newton’s First Law.
If the resultant force on an object is zero, the object remains at rest or continues to move at a constant velocity.
State Newton’s Second Law.
The acceleration of an object is directly proportional to the resultant force and inversely proportional to its mass.
Equation: F = m \times a
State Newton’s Third Law.
For every action, there is an equal and opposite reaction.
What is the equation for weight?
W = m \times g
• W = weight (N)
• m = mass (kg)
• g = gravitational field strength (N/kg)
What is the difference between mass and weight?
•Mass is the amount of matter in an object (kg), it stays constant.
•Weight is the force acting on that mass due to gravity (N), it varies with gravitational field strength.
What is the resultant force?
The single force that has the same effect as all the forces acting on an object combined.
What is the equation for work done?
W=F x d
• W = work done (J)
• F = force (N)
• d = distance moved in the direction of the force (m)
What is the equation for force involving spring extension?
F = k x e
• F = force (N)
• k = spring constant (N/m)
• e = extension (m)
What is Hooke’s Law?
The extension of a spring is directly proportional to the force applied, as long as the limit of proportionality is not exceeded.
What are levers and gears used for?
To transmit the rotational effect of a force and make work easier by multiplying the moment.
How is pressure in a fluid calculated?
p = h x P x g
• p = pressure (Pa) • h = height of fluid (m) • P= density (kg/m³) • g = gravitational field strength (N/kg)
Why does pressure increase with depth in a liquid?
Because the weight of the liquid above increases, so the force per unit area increases.
What is terminal velocity?
The maximum velocity an object reaches when the drag force equals the weight, and acceleration becomes zero.
What is inertia?
The tendency of an object to remain at rest or in uniform motion unless acted on by a force.
What is the law of conservation of momentum?
In a closed system, the total momentum before an event is equal to the total momentum after the event.
What safety features use momentum principles?
Seatbelts, airbags, and crumple zones increase the time over which momentum changes, reducing force and injury risk.
