Forces Flashcards
When work is done on an object, what is equal to the amount of work done?
Energy transferred
How many Nm are in 1J?
1
What is the word for a turning effect of a force?
Moment.
Moment: when a force is balanced, what is equal?
The total clockwise moment and the total anticlockwise moment.
Why does atmospheric pressure change with altitude?
As altitude increases:
1. The number of air molecules decreases
2. The weight of the air decreases
3. There is less air above a surface
How does a lever reduce the amount of force needed to create a moment?
By increasing distance from pivot.
What is the same about the interaction pair of forces when acting on the same object?
Forces are the same size. When forces interact, they exert the same amount of force onto the object.
What is different about the interaction pair of forces when acting on the same object?
Forces act in opposite directions.
What can be used to measure the weight of an object?
Newtonmeter.
How can you find distance travelled by an object on a velocity-time graph?
Calculating the area of the shape formed under the line on the graph.
What is Newton’s FIRST law?
If the resultant force acting on an object is 0N, the object either:
1. Remains stationary
2. Moves at a constant speed
What is Newton’s SECOND law?
The acceleration of an object is:
1. Proportional to the force.
2. Inversely proportional to its mass.
What is ‘inertial mass’?
A measure of how difficult it is to change the velocity of an object.
What is Newton’s THIRD law?
When two objects interact, the forces exerted are equal in size and opposite in direction.
What is stopping distance?
Thinking distance + braking distance
Why is a large deceleration potentially dangerous?
Can lead to overheating of braking or loss of control of vehicle.
What is the link between braking force and vehicle speed and deceleration?
Positive correlation (as one increases, so does the other)
What is meant by ‘conservation of momentum’?
In a closed system, initial momentum is equal to that of momentum after the event.
How does a change in momentum occur?
When a force acts on a moving object (or an object that has potential to move)
What is stopping distance?
Thinking distance + braking distance
Name 2 things that would affect braking distance.
- Wet or icy roads
- Poor tyre condition
Etc.
Name 2 things that would affect thinking distance.
- Intoxication - alcohol or drugs
- Tiredness
- Distractions
Etc.
On a distance-time graph, what does the gradient represent?
The speed
On a velocity-time graph, what does the gradient represent?
The acceleration
What is the typical walking speed?
1.5m/s
What is the typical running speed?
3m/s
What is the typical cycling speed?
6m/s
What is the typical speed of a car?
25m/s
What is the typical speed of an aeroplane?
250m/s
What is the typical speed of sound in air?
330m/s
What is a fluid?
A substance that can flow
What pressure acts (upwards) on an object that is submerged in a fluid?
Upthrust
Why do objects sink?
If their weight is greater than the upthrust force
Why do objects float?
If their weight is equal to the upthrust force.
What is an upthrust equal to?
The weight of the fluid displaced
Why does pressure in a liquid increase with depth?
Pressure is due to the weight of the liquid above a point.
What is atmospheric pressure caused by?
Air molecules colliding with a surface
Why does atmospheric pressure decrease with altitude?
The density of the air decreases - there are fewer air molecules as you go higher.
Less weight of air -> fewer molecules -> density decreases.
Is speed a scalar or vector quantity?
Scalar
Is velocity a scalar or vector quantity?
Vector
What does a straight line on a velocity-time graph represent?
Constant acceleration
What does a curved line on a velocity-time graph represent?
Changing acceleration
What does a horizontal line on a velocity-time graph represent?
Constant velocity
What does an upwards curve on a distance-time graph represent?
Acceleration
What does a downward curve on a distance-time graph represent?
Deceleration
What does a horizontal line on a distance-time graph represent?
Stopping
What is terminal velocity?
The constant velocity a falling object reaches when the resistive force acting on it is equal to its weight.
How can you reduce drag on a moving object?
Streamlining
What does the area under a line on a velocity-time graph represent?
Displacement
