3.4.1 - Mechanics Flashcards
What are some examples of scalar quantities?
distance, speed, mass, temperature
What are some examples of vector quantities?
displacement, velocity, force/ weight, acceleration, energy
How do you calculate moments?
force x perpendicular distance to line of action of force from the point
What are the units of moments
Nm
what can a couple NOT do?
produce translational motion
How do you find the moment of a couple?
force x perpendicular distance between the lines of action of forces
What does the principle of moments state?
for an object in equilibrium, the sum of anticlockwise moments about a pivot is equal to the sum of clockwise moments
What does it mean if an object is described as uniform?
its centre of mass is exactly at the centre
What is the gradient of a displacement-time graph equal to?
velocity
How do you find the average velocity?
divide the final displacement by the time taken
How do you find the velocity from an acceleration-time graph?
area under the graph
How do you find acceleration from a velocity-time graph?
the gradient
How do you find displacement from a velocity-time graph?
area under the graph
What is free fall?
when an object experiences only an acceleration of g (approx. 9.81ms^-2)
What do frictional forces do?
convert kinetic energy into other forms, such as heat and sound
How can we see terminal speed with a skydiver?
As they leave the pane, they accelerate because their weight is greater than the air resistance. As the skydiver’s speed increases, the magnitude of air resistance also increases. This continues until the force of weight and air resistance become equal, at which point terminal velocity is reached.
How does air resistance affect the horizontal and vertical projectile motion?
the maximum height is reached earlier and both the vertical and horizontal distances travelled decrease
What is true of momentum?
it is always conserved in any interaction where no external forces act, so the momentum before an event = the momentum after.
What is force equal to?
the rate of change of momentum
What is impulse and what is its equation? Where is it found on a force-time graph?
it is the change in momentum
F x t
the area under the graph
What is Newton’s first law?
An object will remain in its current state of motion, unless acted on by a resultant force.
What is Newton’s second law?
The sum of the forces acting on an object is equal to the rate of change of momentum of the object.
What is Newton’s third law?
Every action has an equal and opposite reaction.
What is the principle of moments?
For an object to be in equilibrium, the sum of the clockwise moments acting about a point must be equal to the sum of the anticlockwise moments acting about the point.
What makes a pair along with a parachutist’s weight?
the gravitational force of the parachutist on the earth
What is an elastic collision?
Where momentum and kinetic energy are both conserved
What is an inelastic collision?
Momentum is conserved but kinetic energy is not
