Forces and motion Flashcards
What is distance?
- total length of the path travelled by a moving object from start to finish
What is displacement?
- the shortest distance between the start and finish points of a moving object
What types of quantities are distance and displacement?
- distance = scalar
- displacement = vector
What happens to the displacement of an object if they start and end at the same place?
- it will be zero
Can displacement have a negative value?
- yes, depends on the direction moved
What factors could affect the speed of someone walking, running or cycling?
- age
- terrain
- fitness
- distance travelled
What kind of quantity is speed?
scalar
What is the typical speed of a person walking in m/s?
1.5 m/s
What is the typical speed of a person running in m/s?
3 m/s
What is the typical speed of a person cycling in m/s?
6 m/s
What is the typical speed of a car in m/s?
13-31 m/s
What is the typical speed of a train in m/s?
50 m/s
What is the typical speed of a plane in m/s?
250 m/s
What is the typical speed of sound in m/s?
330 m/s
How do you calculate distance travelled?
distance travelled = speed x time
s = v x t
distance in metres
speed in m/s
time in seconds
What is velocity?
speed in a given direction
How could velocity be influenced by defining the direction?
car driving 20m/s to the right
car driving -20m/s to the right (the car is heading left)
Why does the velocity constantly change when an object moves in a circle?
- direction constantly changes
- constant speed, changing velocity
How do you calculate the gradient/ speed of an object using a distance-time graph?
speed/ gradient = change in distance/ change in time
How do you find the speed of an accelerating object in a distance- time graph?
- draw tangent to the graph
- find gradient of tangent
How do you calculate acceleration?
acceleration = change in velocity/ time taken
a = m/s^2
∆v = m/s
t = s
describe the movement and forces of an object falling through a liquid
- initially accelerates
- velocity increrases = drag increases
- resultant force = 0
- object moves at constant speed in one direction
- constant speed = terminal velocity
What is terminal velocity?
the highest speed an object can go under a certain condition
Describe the forces acting on a skydiver that jumps out of an aeroplane
1) maximum acceleration, no drag. large downwards resultant force (jump)
2) accelerates at decreasing rate, drag < weight, small downwards resultant force (1 min of free fall)
3) reaches terminal velocity, drag = weight, no resultant force
What does a straight line upwards represent in a velocity-time graph?
- object accelerates and speeds up
What does a curved line represent in a velocity time graph?
- acceleration decreases
What does a horizontal line represent in a velocity- time graph?
- terminal velocity reached
- acceleration = 0
