FORCES & ENERGY Flashcards
(38 cards)
What is the difference between scalars and vectors?
Scalars have magnitude only, whereas vectors have both magnitude and direction.
How do you calculate the horizontal component of a vector?
X = R cos θ
How do you calculate the vertical component of a vector?
Y = R sin θ
How do you find the resultant vector?
θ = arctan(Y/X), R = √(X² + Y²)
What should free-body diagrams contain?
All forces acting on an object but not any forces exerted by the object itself.
What do three coplanar forces in equilibrium form?
A closed loop - triangle of forces.
How does weight act on an object on an inclined plane?
Weight acts straight down, while the normal reaction acts at a right angle to the plane.
What is the formula for moments?
moment = force × perpendicular distance from the line of action of the force to the pivot, Unit: N m
What does the principle of moments state?
For a body to be in equilibrium, the sum of the clockwise moments about any point must equal the sum of the anticlockwise moments about that point.
What is a couple in physics?
A pair of coplanar forces of equal size acting parallel to each other but in opposite directions.
What is the moment of a couple?
moment of couple = F × distance between forces
What is the center of mass of a body?
The point through which a single force on the body has no turning effect.
What happens to a body in stable equilibrium when displaced?
It returns to its original position because the center of mass is directly below the point of support.
What happens to a plank on a drum when displaced?
It will roll off the drum because the center of mass is directly above the point of support.
What is the condition for an object to topple?
The line of action of its weight must pass beyond the pivot.
What does the gradient of a displacement-time graph represent?
Velocity.
What does the gradient of a velocity-time graph represent?
Acceleration.
What is the equation for uniform acceleration?
v = u + at, s = ut + 1/2 at², v² = u² + 2as
What does ‘a’ represent in suvat equations?
‘a’ represents acceleration due to gravity, g, which always acts downwards.
How should horizontal and vertical components of motion be considered?
They must be thought of separately.
What happens to the speed of a projectile in horizontal motion?
It remains constant until the projectile lands.
How do you resolve initial velocity into components when launching a projectile at an angle?
X = R cos θ, Y = R sin θ
What is the relationship between resistance and speed?
Resistance is proportional to speed.
What does friction/drag do to kinetic energy?
It converts kinetic energy to heat and sound energy, increasing with speed.
