Motion and Forces Flashcards
In a distance time graph what does it mean if the line is moving at a constant speed in a straight line that slips upwards?
It is moving at a constant speed
What does the gradient of a distance-time graph show?
Represents the objects speed
How can you tell velocity from speed?
Velocity is speed in a given direction
How can you tell from a distance time graph that the object is stationary?
Stationary is a horizontal line
Unit of acceleration?
m/s (squared)
What does the area under the line on a velocity time graph represent?
The distance travelled
If the velocity time graph is a horizontal line what is the acceleration?
0 acceleration
What can forces do?
A force can change the shape of an object or its state
What’s the unit for force?
N (Newtons)
If the resultant force on an object is zero what happens?
The object stays at a constant velocity
If the resultant force on an object is not zero what happens?
The velocity of the object will change
What is acceleration?
The change in velocity (speed) per second
What is the driving force ( engine force/motive force) down to?
It is due to friction between the ground and the tyre of each drive wheel
What is the resultant force?
A single force that has the same effect as all the forces acting on an object
What happens if the resultant force of an object isn’t zero?
The velocity will change
When does the velocity of an object increase ? What type of acceleration is it ?
If the resultant force is in the same direction as the velocity it increases
Positive acceleration
When does the velocity of an object decrease ? What type of acceleration is it ?
If the resultant force is in the opposite direction as its velocity
Negative acceleration
If the resultant force is big what happens to the acceleration?
The acceleration is greater
If the mass of an object is great what happens to the acceleration?
It is smaller for a given force
What two forces are opposite to the driving force of a car?
Friction
Air resistance
What two factors affect the stopping distance?
Thinking distance
Braking distance
What is the thinking distance?
The distance travelled by the vehicle in the time it takes the driver to react
What factors increase the thinking distance?5
Tiredness
Alcohol
Drugs
Mobile phone use
Increasing the speed
How can you work out the thinking distance?
when you are given the drivers reaction time and speed
cars speed x reaction time
What is the breaking distance?
The distance travelled by the vehicle during the time the braking force acts
What increases the breaking distance?
Poor weather conditions
Poor car maintenance e.g. Worn tires
If the speed increases
What is the weight of an object?
The force of gravity on it
What do weight measured in?
N
What is mass?
The quantity of matter in it
What is mass measured in?
KG
How much gravitational field strength does the earth have?
Roughly 10 N/Kg
What is the unit of gravitational field strength?
N/Kg
What increases drag force?
Speed
What happens when an object falls in a fluid?
The fluid drags on the object
What happens when an object falls through the air?
The drag force is air resistance
What happens to the acceleration of an object and why?
The acceleration of the object decreases as it falls
because the drag force increases as it speeds up
When does an object reach a constant velocity (speed)? & what is its name?
When the drag force on it is equal and opposite to the weight
Terminal velocity
If the resultant force is zero what is the acceleration?
Zero too
What type of component shows a change in temperature?
A thermistor
Why would the current passing through each element be the same?
It is a series circuit and therefore the current is the same throughout
Because of forces, explain why the parachutist reached a terminal velocity and why opening the parachute reduces the terminal velocity?
1 when he left the airplane the force acts downwards
2 as the parachutist falls air resistance acts upwards
3 the weight is greater than the air resistance
4 as the velocity and speed equal eachother he reached terminal velocity
5 opening the parachute increased his surface area increasing the air resistance
6 air resistance is greater than the weight
7 the resultant forces slow down and when they are equal he reaches terminal velocity
What does the mass of an object have to do with its acceleration?
The greater the mass the smaller acceleration
What are the opposite forces of the driving force of a car?
Friction and air resistance
What is the unit of gravitational field strength?
N/kg
What increased drag force?
Speed