Mechanics 2 - Linear and Projectile Motion Flashcards
What is displacement and how is it different to distance?
Displacement is a measure of the line connecting the starting point to the finishing point.
Distance is a measure of the total length of the path travelled.
Also distance is a scalar and displacement is a vector.
What does a straight line on a distance-time graph represent?
A constant speed.
How is acceleration defined?
Acceleration is the rate of change of velocity.
How is speed different to velocity?
Speed is the rate of change of distance.
Velocity is the rate of change of displacement.
Describe the motion of this ball
Ball is moving to the right and speeding up.
Decribe the motion of this ball.
Ball is moving to the left and speeding up.
Describe the motion of this ball.
Ball is moving to the right and slowing down.
Describe the motion of this ball.
Ball is moving to the left but slowing down.
Is the ball moving to the right?
Only if the velocity vector is also acting to the right.
What does a straight line on a displacement-time graph represent?
A constant velocity.
What does a curve with an increasing gradient represent on a displacement-time graph?
An increasing velocity (acceleration)
What does a curve with a decreasing gradient represent on a displacement-time graph?
A decreasing velocity (decceleration)
What does a negative gradient on a displacement-time graph represent?
A negative velocity (travelling back to where it started)
What does a straight line on a velocity-time graph represent?
A constant acceleration.
What does a curve with an increasing gradient represent on a velocity-time graph?
An increasing acceleration.
What does a curve with a decreasing gradient represent on a velocity-time graph?
A decreasing acceleration.
What does a negative gradient on a velocity-time graph represent?
A negative acceleration.
What does this graph show?
A ball bouncing off a surface
(Dotted lines represent the bounce)
(Red lines represent the ball accelerating towards the ground)
What does the acceleration time graph of a ball in freefall look like?
Constant acceleration of 9.81ms-2
What does the area of a speed-time graph represent?
How about a velocity-time graph?
What’s wrong with this?
Displacement takes direction into account.
It should be…
When can you use this equation?
When the acceleration = 0 (constant velocity)
Or to work out an average speed
When can you use SUVATs?
When acceleration is constant
Or if object has stages of constant acceleration
Why can’t you use SUVAT’s when working with this graph?
Because the acceleration (gradient) is changing
What does it mean if an object is in freefall?
Only weight is acting on the object
It has a constant acceleration of 9.81ms-2 acting downawards (on Earth)
If one ball is dropped as another is projected horizontally which hits the ground first?
They both hit the ground at the same time…
Both in freefall so accelerate at 9.81ms-2
Vertical motion independent of horizontal motion
What’s wrong with this labelling?
Initial velocity and final velocity are not 0
In projectile motion when is the vertical component of the velocity 0?
At the peak of a parabola
Not at the start or end
How do you start a question involving angled projectile motion?
Resolve the velocity into vertical and horizontal components and fill out the corresponding SUVATs
What is wrong here?
The acceleration is only 9.81ms-2 if the object is in freefall
