P4 - Explaining Motion Flashcards
what is a force?
is a push or pull, on an object, that is caused by it interacting with another object
why are forces considered vector quantities?
both have direction and magnitude (newtons)
what is the normal contact force?
are the “push” forces that two touching objects always exert on each other
what is newton’s third law?
when two objects interact, the forces they exert on each other are equal (magnitude) and opposite (direction)
what is mass?
it’s the amount of matter in an object
measured in kg
what does everything with mass have?
everything that has mass has a gravitational field around it
what is weight?
when an object is on a planet a downwards force acts on the object due to gravitational attraction between the object and planet
how can you calculate weight?
weight (N) = mass (kg) x gravitational field strength (N/kg)
what does gravitational field strength equal on the earth?
g = 10N/kg
what are scalar quantities?
are just numbers, they simply tell you the “size” or magnitude of the thing you’re measuring
name some examples of scalar quantities?
speed, distance, time, mass
what are vector quantities?
tells you both the size and direction
what are some examples of vector quantities?
force, velocity, displacement, and acceleration
what are vectors usually represented by??????
by an arrow, the length of the arrow shows the magnitude, and the direction of the arrow shows the direction of the quantity
what are the 3 ways the motion of the object can be described?
speed, direction, and whether its speed is changing
what is speed?
is how fast the object is going, with no regard to direction
what is velocity?
is the speed of the object in a given direction
what is the speed, distance, time formula?
average speed (m/s) = distance (m) ÷ time (s)
what is acceleration?
is the change of velocity of an object in a certain amount of time
if an object accelerates, is must be?
speeding up or changing direction
how can you find the average acceleration?
acceleration (m/s²) = change in speed (m/s) ÷ time taken (s)
how do you work out speed from a distance time graph?
the gradient of a specific point of the graph is the speed
use the ∆ distance / ∆ time for the speed
how do you work out the speed/gradient of acceleration or decertation on a distance-time graph?
you draw a tangent in line with the curve
you choose 2 points on the tangent and calculate the ∆ in distance and time and divide both changes ∆
what does the gradient on a velocity time graph tell us?
acceleration
what is the formula for the area of a triangle?
1/2 base x height
how can you work out the distance in a velocity time graph?
work out the area of inside the curve
what are freebody diagrams?
show all the forces acting on a object
what is a resultant force?
if you have a number of forces acting at a single point, you can replace them with a single force that takes in account the sizes and directions of all the forces added together
what force does weight of an object create?
gravity??
how to use scale drawings to find the resultant force?
draw all the forces acting on a object, to scale, “tip to tale”
then draw a straight line from the start force to the end of the last force; the resultant force
if all the forces acting on an object combine to give a resultant force of zero, the object is in??
equilibrium
what does Newton’s first law say?
a resultant force is needed to change the motion of an object
what does Newton’s first law say about an object travelling in a straight line?
if the resultant force on a moving object is zero, it will just carry on moving at a constant speed in a straight line
what does Newton’s first law say about stationary objects?
if the resultant force on a stationary object is zero, the object will remain stationary
what are the 3 things that could happen when a non-resultant force acts on an object?
- object will accelerate if the force is in the same direction as the object’s motion
- the object will slow down if the force in in the opposite direction to the object’s motion
what is Newton’s second law?
non-zero resultant force acts on an object, then it will cause the object to accelerate
what is F = m x a
force (N) = mass (kg) x acceleration (m/s²)
what is inertia?
the tendency for the motion of an object to remain unchanged
