Force, Energy And Momentum Flashcards
What is the difference between scalar and vector quantities
Scalars describe only a magnitude while Vectors describe magnitude and direction
What are some examples of scalar quantities
Distance speed mass and temp
What are some examples of vector quantities
Displacement velocity force/weight and acceleration
How do you find the resultant force of two perpendicular forces
Use Pythagoras
How do you find the direction of two perpendicular forces
Trigonometry
What type of diagram should be drawn to show two forces that are not perpendicular
A scale drawing
For an object to be in equilibrium the sum of all the forces acting on it should add up to what
0
Does an object in equilibrium have a resultant force and what does that mean about the motion of the object
It has no resultant force so the object is either at rest or moving at a constant velocity
What are the two ways of showing an object is at equilibrium
Adding the horizontal and vertical components of the forces acting on it showing they equal to 0
Or if there are 3 forces acting on it draw a scale diagram if the scale diagram forms a closed diagram then the object is in equilibrium
What is the equation for a moment
Moment = force x perpendicular distance to line of action of the force from the point
What is a couple
Is a pair of coplanar forces( forces that act in the same plane) where the two forces are equal in magnitude but act in opposite directions
How do you find the moment of a couple
Moment of a couple = force x perpendicular distance between the lines of action of forces
What does the principle of moments state
That for an object in equilibrium, the sum of the anti-clockwise moments about a pivot is equal to the sum of the clockwise moments
What is the centre of mass of an object
Is when an object is balanced at a particular point this means at this point the object does not turn meaning all the weight on one side of the pivot is equal to the weight on the other side of the pivot
What does it mean if an object is described as uniform
The centre of mass is exactly at its centre
What is speed
How quickly an object is travelling
What is displacement
The overall distance travelled from the starting position
What is velocity
Rate of change of displacement
what is acceleration
rate of change of velocity
what is instantaneous velocity and how can it be found
is the velocity of an object at a specific point in time
it can be found from a displacement time graph by drawing a tangent to the graph at the specific time and calculating the gradient
what is average velocity and how can it be found
is the velocity of an object over a specified time frame it can be found by dividing the final displacement by the time taken
what is uniform acceleration
where the acceleration of an object is constant
what do acceleration time graphs represent and what does the area under the graph equal
represents the change in acceleration over time and the area under the graph equals the change in velocity
what do velocity time graphs represent and what does the gradient and area under the graph equal
represent the change in velocity over time and the gradient equals acceleration and the area under the graph equals displacement
what do displacement time graphs represent and what does the gradient equal
shows the change in displacement and the gradient equals velocity
what equations can you use when an object is moving at uniform acceleration
SUVAT’s
are the vertical and horizontal components of projectile motion dependent or independent
independent
how do you calculate projectile motion
calculate horizontal and vertical components separately using the uniform acceleration formula
what is free fall
where an object experiences an acceleration of g
what is friction and what else is it known as
a forces which opposes the motion of an object and can be known as drag or air resistance
when does the magnitude of air resistance increase
when the speed of the object increases
what is lift and what it caused by
is an upwards force which acts on an object travelling in a fluid and is caused by the object creating a change in direction of fluid flow
when does terminal speed occur
occurs where the frictional forces acting on an object and driving forces on an object and so there is no resultant force so no acceleration so the object travels at a constant speed
what is an example of an object reaching terminal speed
- as they leave the plane 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
what does air resistance affect in projectile motion
the horizontal and vertical components as the max height is reached quicker and it doesn’t travel as far or as high
what is newtons first law
an object will remain at rest or travelling at a constant velocity until it experiences and external resultant force
what is newtons second law
the acceleration of an object is proportional to the resultant force experienced by the object F = M A
what is newtons third law
for each force experienced by an object the objects exerts an equal and opposite force
what is momentum
is the product of mass and velocity of an object
what is impulse
is the change in momentum
what is force
the rate of change of momentum
on a force time graph what is the area under the graph equal to
the the change in momentum
what are the two types of collisions
elastic and inelastic
what is an elastic collision
where both momentum and kinetic energy is conserved
what is inelastic collision
where only momentum is conserved while the kinetic energy is converted into other forms
what makes it an inelastic collision
when the object in a collision stick together after the collision
what is work done
the force causing a motion multiplied by the distance travelled in the direction of the force
what does the rate of doing work equal
the rate of energy transfer
what is power
the rate of energy transfer
what is the area of a force displacement graph equal to
work done
what is efficiency
is a measure of how efficiently a system transfers energy
what is the principle of conservation of energy
that energy cannot be created or destroyed but can be transferred from one form to another
if the total energy is in a closed system does the energy stay constant
yes
what is an example of conservation of energy
the thrower gives the ball kinetic energy therefor it moves upwards, however as it does the ball slows down because kinetic energy is being transferred to gravitational potential energy
- eventually, all the kinetic energy is transferred to gravitational potential energy and the ball stops momentarily, after which the ball’s gravitational potential energy is converted back into kinetic energy and the ball falls to the ground
