Unit 1 Forces and Motion Flashcards
What is a distance time graph?
A graph in which measures how far something travels in a certain period of time, and the different speeds that occur at different stages.
What does the gradient of a line represent in a distance time graph?
The speed of which the object is travelling at
What is the formula for speed?
change in distance/change in time = speed
s = d/t
What does a straight diagonal line represent in a distance time graph?
Constant Speed
What does a straight horizontal line represent in a distance time graph?
Stationary
What is the speed of an object that is stationary?
0m/s
We know this because the gradient of a straight horizontal line is 0 in a distance time graph (gradient = speed)
What does a curve up mean in a distance time graph?
Acceleration: Gradient/Speed is increasing
Changing speeds
What does a curve down mean in a distance time graph?
Deceleration: Gradient/Speed is decreasing
Changing speeds
How do you find the gradient of a curve in a distance time graph?
You can draw a tangent (a straight line on the curve) and figure out the gradient from the line onwards.
Which axis do the distance and time go in a distance time graph?
Time = x axis
Distance = y axis
What is the formula for acceleration when you are given the time?
acceleration (m/s2) = change in velocity (m/s) / time (s)
How can you find the change in velocity?
v - u
final velocity - initial velocity
Is acceleration a vector or scalar quantity? What does this mean?
Vector quantity
Meaning it have a number and a direction. We show the direction by using negative or positive numbers.
Positive = Accelerating
Negative = Decelerating
When you calculate the acceleration, is it accurate?
No, because it is just the average velocity in that period of time.
If the line in the distance time graph was straight diagonal - that means it is constant. Meaning that the rate of acceleration is the same throughout.
But if the line were a curve then the rate of acceleration wouldn’t be the same throughout. It could be different velocities at different stages averaged out together.
What is acceleration?
The rate of change in velocity. How quickly something can speed up or slow down.
What is the formula for acceleration when you are given the distance/
2a (m/s2) s (m) = v2 - u2 (m/s)
What is the a velocity of an object that’s initial velocity is stationary?
0m/s
What is a velocity time graph?
A graph that measures how an objects velocity changes overtime.
In a velocity time graph, which axis do the velocity and time go?
Velocity = y axis
Time = x axis
What does the gradient represent in a velocity time graph?
acceleration = change in velocity/change in time
What does a constant positive gradient represent (upwards diagonal line) in a velocity time graph?
Constant acceleration
What does a constant negative gradient represent (downwards diagonal line) in a velocity time graph?
Constant deceleration
What does the flat sections represent in a velocity time graph?
Constant velocity
How do you calculate the distance travelled in a velocity time graph?
By finding the area under the curves/lines - answer in meters.
*To calculate area under curve lines just count the boxes that make up the area - not accurate but it’s fine.
What is the formula for weight?
w = m x g
weight = force
g = 9.8N or 10N
What do forces do to objects?
forces can change the speed (accelerate), the shape (stretch/compress) and the direction of objects
What are the types of forces?
gravitational force, electrostatic force, frictional force, applied force, tension force and normal force
What is gravitational force?
the force of attraction between 2 objects mass
What is electrostatic force?
the force between electrically charged objects
What is frictional force?
the force opposing the motion of objects when rubbed together
What is applied force?
force exerted by a person/object
What is normal force?
force exerted by the surface to support the weight of the object on it
What is tension force?
force transmitted by a string when pulled on both ends
What force a vector or scalar quantity?
vector quantity because it have a magnitude and direction
What is the resultant force?
total amount of force acting on an object along with the direction
What is the resultant force of an object at rest?
0N
How do you calculate the resultant force?
add all the magnitudes if the forces are in the same direction. however if the forces are in different directions subtract the magnitudes.
What is friction?
the force that acts between 2 surfaces when in contact with each other. it opposes motion between them and can slow it down.
What does the force of friction depend on?
the normal force acting on it pushing them together
What is stopping distance?
the time it takes for a driver to stop their car when it finds out it needs to
What is the formula for stopping distance?
stopping distance = thinking distance + braking distance
What is the thinking and braking distance?
thinking distance: distance travelled during the drivers reaction time realising to stop
braking distance: distance travelled from when the driver applied brakes to when the car stops.
What are the factors affecting stopping distance?
speed, mass, road conditions, reaction time
What is Hooke’s law?
force and extension are directly proportional up until the elastic limit
What is the formula for Hooke’s law?
force = spings constant x springs extension
f=kx
What is elastic behaviour?
the ability of an object to go back to its original shape after the forces applied causing deformation have been removed. this is because the particles in the material can act like springs.
What is the elastic behaviour for helical springs?
springs are elastic and always come back to original shape after the forces are removed. however only up until the elastic limit, this is the point where too much force is applied and the spring come back longer than it was before.
What is the elastic behaviour for metal wires?
a metal wire will go back to its original shape except if the force applied exceeds its elastic limit - it will break. (breaking point)
What is the elastic behavior for rubber bands?
a rubber band will go back to its original shape except if the force applied exceeds its elastic limit - it will break.
