topic 2 - motions and forces

motion and forces

what are scalar quantities?

quantities that have a size or magnitude

but no direction

what are vector quantities?

quantities that have a size or magnitude

with direction

what is the difference between speed and velocity?

velocity is speed but with direction

speed equation

speed = distance/time

what is acceleration?

the change in velocity per second

acceleration equation

acceleration = change in velocity/time taken

velocity equation

(final velocity2) - (initial velocity2) = 2 x acceleration x distance

what is the core method for the practical that determines speed

1. measure the length of card interrupt attached to the trolley using a metre ruler

2. position two light gates along the ramp at a measured distance apart

3. release the trolley from a fixed starting position at the top of ramp from rest

4. as the trolley passes through the light gate, the light gate measures the time taken for the card to interrupt the light beam

5. calculate speed using equation speed = distance/time

for speed practical, what are the independent variables?

distance travelled

height of ramp

for speed practical, what are the dependent variables?

time taken

calculate speed

for speed practical, what are the control variables?

starting position for trolley

mass of trolley

slope’s angle

what is newton’s first law?

a body will remain stationary or continue in a straight line at a constant speed as long as the forces acting on it are balanced

when the resultant force is 0, if the object is stationary,

it stays at rest (doesn’t move)

when the resultant force is 0, if the object is moving,

it continues to move at a constant speed in a straight line

when the resultant force is not 0, it means that there’s _______ resultant force acting on the object, which means…

unbalanced

it’s velocity will change, meaning it will accelerate (in the direction of resultant force)

a non-zero resultant force can cause an object to:

speed up

slow down

change direction

what’s newton’s second law?

1. when a resultant force acts on a mass then there will be a change in it’s velocity.

2. the resultant force determines the size and direction of the subsequent acceleration of the mass

for size (how big the acceleration is):
a bigger resultant force = …. because
a bigger mass = ….. because

bigger acceleration because the object speeds up or slows down faster
smaller acceleration because it’s harder to move heavier objects

what’s another way of calculating acceleration (using force and mass)

acceleration = force/mass

what is inertial mass?

a measure of how difficult it is to change the velocity of a moving object