Topic 3 - Motion And Forces Flashcards
What is speed?
How FAST you are going with NO regard to direction
What are speed and velocity measured in?
m/s(or km/h or mph)
What is velocity?
How fast you are going WITH regard to direction. The distance in a particular direction is called displacement.
What is displacement
The distance in a particular direction
Velocity and displacement depend on what?
SIZE and DIRECTION
What is acceleration?
How quickly a velocity is changing
How is the change in velocity effected?
Change in SPEED or change in DIRECTION (or both)
Is acceleration a vector quantity?
Yes
How do you calculate the speed of a distance-time graph?
Find the gradient- vertical / horizontal
How to find acceleration of velocity time graph
Find gradient = y / x = vertical / horizontal
Forces on a stationary object?
- Gravity/weight (down)
- Reaction force (pushing up)
(They are equal)
Forces on steady horizontal velocity with forces in balance
Thrust (forward)
Drag (backward)
Gravity/Weight (down)
Reaction (up)
Forces on steady vertical velocity with forces in balance
Drag (up)
Weight/Gravity (down)
Forces on horizontal acceleration with forces unbalanced
Only acceleration arrow labelled (forward)
Put arrows around car but no words except ‘acceleration’
Forces on vertical acceleration with forces unbalanced
Less drag (upwards)
More weight (down) and acceleration (down)
What is weight caused by and what is it measured in?
Caused by pull or gravity, and it’s a force measured in newtons
Is mass a force?
NO!
What is mass? What is it measured in?
How much ‘stuff’ in an object, measured in kg
If you go to the moon, what is changed: your mass or your weight?
Your mass stays the SAME. Your weight CHANGES
Falling object in a vacuum fall at the same rate or a different rate?
The SAME rate
Why do falling objects in a vacuum accelerate at the same rate?
Because space (a vacuum) has no air resistance, so there is no resistance to slow down falling objects - the only acting force on an object is gravity.
Objects falling through and atmosphere reach a what?
Terminal velocity
Why do objects falling through an atmosphere reach a terminal velocity?
- When falling objects first set off, they have more force (weight/gravity) accelerating them than air resistance slowing them down
- As speed increases, air resistance increases
- Air resistance gradually increases and reduces the acceleration until it is equal to weight and gravity of falling object
- When two forces are balanced, the object will not accelerate any more. It will have reached maximum speed - its terminal velocity.
When two bodies interact, what happens to the force?
They exert force onto eachother
If object A exerts force on Object B, what happens next?
Then object B exerts the exact opposite force (but same size) on object A.
No resultant force means what for velocity?
No change in velocity
To keep a steady speed of an object there should be how much resultant force?
ZERO! NONE!
What does resultant force mean?
Acceleration
If the resultant force acting on a body is not zero, it will accelerate in what direction?
The direction of the resultant force
What happens to the acceleration or deceleration when the resultant force is big?
Acceleration and deceleration will be greater
If there’s an overall force, the object will..
Accelerate
It the object has a steady speed, the forces are…
Balanced
Difference between speed and velocity?
Velocity is a vector, speed is not
When all the forces on an object are balanced, what is the resultant force?
0
How does doubling the size of the resultant force effect the acceleration?
The acceleration also doubles
How does doubling the mass of an object effect the acceleration?
The acceleration halves
What is the gravitational field strength of the Earth?
10 N/kg
What is gravitational field strength measured in?
N/kg
What are the three stages of falling?
- At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards.
- As it gains speed, the object’s weight stays the same, but the air resistance on it increases. There is a resultant force acting downwards.
- Eventually, the object’s weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity.
What are the two forces that affect a falling object?
Weight of object
Air resistance
