Forces and their Effects Flashcards
What do distance-time graphs show?
Something travelling through time and space.
How is speed represented on a distance-time graph?
Through the gradient.
What does a flat section on a distance-time graph represent?
A stationary period.
What do uphill and downhill sections on a distance-time graph represent?
Periods when the object is moving.
What is the link between the gradient of a line on a distance-time graph and how fast the object was moving?
The steeper the gradient the faster the object was moving.
What does a downhill section on a distance-time graph represent?
The object moving towards its starting position.
What does a curve on a distance-time graph represent?
Acceleration or deceleration.
What is speed?
How quickly an object is moving.
What is velocity?
Speed in a given direction.
What is acceleration?
How quickly velocity is changing.
What is the formula for acceleration?
v - u
a= ——
t
a= acceleration (m/s squared)
v= final velocity (m/s)
u= initial velocity (m/s)
t= time (s)
What does the gradient represent on a velocity-time graph?
Acceleration
What does a flat section on a velocity-time graph represent?
Steady speed
What is the link between the gradient of a line on a velocity-time graph and the acceleration of the object?
The steeper the gradient, the greater the acceleration or deceleration.
What does an uphill section on a velocity-time graph represent?
Acceleration
What does a downhill section on a velocity-time graph represent?
Deceleration
What does a curve on a velocity-time graph represent?
A change in acceleration.
How can one work out the distance travelled from a velocity-time graph?
Work out the area under the line on the graph to find the distance in metres travelled.
What is a resultant force?
The force that decides the motion of an object. If there are several forces working on the object, the resultant force tells us what the overall effect is.
What will the result of a non-zero resultant force be on an object?
A change in velocity (acceleration or deceleration)
What is a force diagram?
A diagram that shows all the forces acting on an object at once as well as their directions and relative sizes - the larger the arrow the larger the force.
How do you work out the resultant force?
1) Set a direction (generally forward) as positive.
2) Add up the total forces acting in the positive direction.
3) Add up the total forces acting in the opposite direction.
4) Subtract all the forces acting in the opposite direction from the forces acting in the positive direction.
What happens if the resultant force on a stationary object is zero?
The object will remain stationary.
What happens if the resultant force on an object isn’t zero?
The object will accelerate in the direction of the resultant force.
What happens if the resultant force on a moving object is 0?
It will continue to move at a constant velocity.
What happens if the resultant force on a moving object isn’t 0?
The object will accelerate in the direction of the resultant force.
What are the five types of acceleration that can take place as a result of resultant forces?
- Starting
- Stopping
- Changing direction
- Speeding up
- Slowing down
What is the formula that allows us to calculate acceleration using the resultant force?
F
a = —-
m
a = acceleration (m/s squared)
F = resultant force (N)
m = mass (kg)
What are the two effects of gravity?
- Causes things to accelerate towards the ground.
* It gives everything weight.
What is the difference between weight and mass?
Weight is the force you exert on the ground. It varies between planets.
Mass is constant no matter where you are.
How does one measure weight?
Using a spring balance or newtonmeter.
How is mass measured?
Using a mass balance.
What formula links weight and mass?
W = m x g
W = weight (N)
m = mass (kg)
g = gravitational field strength (N/kg)
What is the gravitational field strength on Earth?
10 N/kg
What is the gravitational field strength on the moon?
1.6 N/kg
What are reaction forces?
Forces that result from one object applying a force to another. It is in the opposite direction to the original ‘action’ force.
What is the law about reaction forces?
For every action, there is an equal and opposite reaction.
If an object has no force propelling if, what will happen?
It will slow down and stop because of friction.
In what direction does friction act?
The opposite direction to the movement of the object.
What is drag?
Friction caused by an object moving through a liquid or gas.
What is a streamlined object?
An object that allows fluids to flow over it easily.
What is the relationship between friction and speed?
The faster the object, the greater the frictional force.
What are two ways of increasing the top speed of a vehicle?
1) Reduce drag by streamlining it.
2) Increase the power of the vehicle’s engine.
Describe terminal velocity.
When an object falls from a large distance, it doesn’t keep accelerating. Instead, it’s acceleration decreases until it reaches a steady velocity - its terminal velocity.
How does terminal velocity occur?
As the object gets faster, the effects of drag become greater as well. After a point, the frictional force is equal to the opposing force so the object will move at a constant velocity.
What two factors affect an object’s terminal velocity?
Shape and area.
What is stopping distance?
The distance covered by a vehicle in the time between the driver spotting a hazard and the vehicle coming to a complete halt.
What is thinking distance?
The distance covered by a vehicle during the time it takes between the driver recognising a hazard and applying the brakes.
What is braking distance?
The distance a vehicle travels after the brakes are applied until the vehicle comes to a complete stop.
What two main factors affect thinking distance?
- The speed of the vehicle.
* How quick to respond the driver is.
What four main factors affect braking distance?
- The speed of the vehicle.
- The quality of the brakes on the vehicle.
- The quality of the tyres on the vehicle.
- How good the grip between the tyres and the road is.
Describe the energy transfer that takes place when brakes are applied.
The kinetic energy in the wheels converts to heat energy in the brakes, causing the temperature of the brakes to increase.
What is an elastic object?
An object that will return to its original shape after a force has been removed from it.
What is elastic potential energy?
Energy stored in an elastic object when a force is applied to it. It is then converted into kinetic energy when the force is removed.
What is the formula to work out the extension of an elastic object?
F = k x e
F = force applied (N)
k = Spring constant (N/m)
e = extension (m)
What is the limit of proportionality?
The point at which an elastic object will no longer extend proportionally with the force applied to it.
