Chapter 2: Kinematics Flashcards
(26 cards)
State the difference between distance and displacement.
Distance is a scalar quantity because it describes how far an object has travelled overall, but not the direction it has travelled in.
Displacement is a vector quantity because it describes how far an object is from where it started and in what direction
Define speed and state its formula.
The speed of an object is the distance it travels every second. Speed is a scalar quantity with magnitude only.
average speed = total distance/time taken
Define velocity and state urs formula
Velocity is defined as the rate of change of displacement. Velocity is, therefore, a vector quantity because it describes both magnitude and direction.
Average velocity = total displacement/time taken
v= ∆x/∆t = (u+v)/2
Define acceleration and state its formula.
Acceleration is defined as the rate of change of velocity.
average acceleration = change in velocity/time taken
∆v = (v-u)
State the 5 types of graphs that can represent motion.
- Distance time graph
- Displacement time graph
- Speed time graph
- Velocity time graph
- Acceleration time graph
Explain about distance time graphs. (4)
The slope is equal to the speed.
A straight line represents constant speed.
A curved line represents acceleration.
The slope is always zero or positive because distance is a scalar quantity.
Explain displacement time graphs (4)
Slope equals velocity.
A straight line represents a constant velocity.
A curved line represents acceleration.
A positive slope represents motion in the positive direction and a negative slope represents motion in the negative direction.
Explain speed time graphs
The slope equals acceleration.
A straight line represents uniform acceleration.
A curved line represents non uniform acceleration.
A positive slope represents increase in speed.
A negative slope represents a decrease in speed.
A zero slope represents motion with constant speed.
The area under the curve equals the distance travelled.
Explain velocity time graphs
The slope equals acceleration.
A straight line represents uniform acceleration.
A curved line represents non uniform acceleration.
A positive slope represents an increase in velocity in the positive direction.
A negative slope represents a decrease in velocity in the negative direction.
A zero slope represents motion with constant velocity.
The area under the curve equals displacement.
Explain acceleration time graphs
The slope is meaningless.
A zero slope represents an object undergoing constant acceleration.
The area under the curve equals change in velocity.
State what is the area under a velocity time graph
Displacement
Area of triangle formula
A=1/2bh
Area of rectangle formula
A=bh
State what the gradient of a displacement time graph shows
velocity
State what the gradient of a velocity time graph shows.
Acceleration
State a summary of the areas under the graph and gradients for the different motion graphs
Gradient:
Displacement-time: velocity
Velocity-time: acceleration
Area under graph:
Velocity-time: displacement
Acceleration-time: velocity
State the four kinematic equations of motion which can describe any object moving with constant acceleration.
v=u+at
s=1/2(u+v)t
s=ut+1/2at^2
v^2=u^2+2as
State what is meant by independent variable.
The variable you change; unaffected by other variables.
State what is meant by dependant variable.
The variable you measure; dependant on other variables.
Explain how the acceleration of free fall experiment works.
The overall aim of the experiment is to calculate the value of the acceleration due to gravity, g. This is done by measuring the time it takes for a ball bearing to fall though a certain distance. The acceleration is then calculated using an equation of motion. Independent variable is the height and the dependant variable is time. Control variables: same steel ball bearing, same electromagnet, distance between ball bearing and top of the glass tube. Don’t forget a cushion underneath the end of the glass tube to catch the ball bearing. Switch the current on the electromagnet and place ball bearing directly underneath so ur is attracted to it. And when starting experiment switch of current. Once completed plot a graph of 2h/t against t and the gradient of the graph will be your value of g.
How to find the time of flight of projectile motion?
Time of flight: how long the projectile is in the air.
u=u sinθ
a=-g
v=0
t=?
v = u + at
0 = u sinθ -gt
t= (u sinθ)/g
2t=2 (u sinθ)/g
If the time to maximum height is t, then the time of flight is 2t.
How to find the maximum height in projectile motion?
Maximum height attained: height at which the projectile is momentarily at rest
v^2=u^2+2as
H=((u sinθ)^2)2g
How to find range in projectile motion?
Range: the horizontal distance travelled by the projectile
distance = speed * time (time from previous calc)
Initial speed = (u cosθ)
R = (u^2 (u sin2θ))/g
Deriving kinematic equations:
v=u+at
Define acceleration:
a=(v-u)/t
Or from the gradient if a velocity time graph
