P5 - Forces Flashcards
What is a force?
A push or a pull on an object caused by its interaction with something.
What are the two types of forces?
Contact forces and non-contact forces.
What is a contact force?
A force that acts when two objects are touching.
Give examples of contact forces.
- Friction
- Air resistance
- Tension in ropes
- Normal contact force
What is a non-contact force?
A force that acts when objects do not need to be touching.
Give examples of non-contact forces.
- Magnetic force
- Gravitational force
- Electrostatic force
What is the definition of a vector quantity?
A quantity that has both magnitude and direction.
Is force a vector or scalar quantity?
Vector quantity.
List some examples of vector quantities.
- Force
- Velocity
- Displacement
- Acceleration
- Momentum
What is a scalar quantity?
A quantity that has magnitude but no direction.
List some examples of scalar quantities.
- Speed
- Distance
- Mass
- Temperature
- Time
What does Newton’s Third Law state?
For every action, there is an equal and opposite reaction.
What force attracts the Sun and the Earth to each other?
Gravitational force.
Describe the normal contact force in relation to a chair and the ground.
A chair exerts a force on the ground, while the ground pushes back at the chair with the same force.
What is Gravitational Force?
The Force of Attraction Between Masses
Gravitational force causes objects to be attracted to planets or stars.
What is the difference between mass and weight?
- Mass is the amount of ‘stuff’ in an object
- Weight is the force acting on an object due to gravity
How does gravitational field strength vary?
It varies with location and is stronger closer to the mass causing the field and for larger masses.
Does the weight of an object change with location?
Yes, the weight of an object depends on the strength of the gravitational field at its location.
What is the weight of a 1 kg mass on Earth?
About 9.8 N
What is weight measured in?
Newtons
What is the formula for calculating weight?
Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg)
What is the approximate value of gravitational field strength (g) on Earth?
9.8 N/kg
What is the approximate value of gravitational field strength (g) on the Moon?
1.6 N/kg
Are mass and weight directly proportional?
Yes, increasing the mass of an object increases its weight.
What happens to weight if mass is doubled?
The weight also doubles.
What is a bearing in the context of forces?
An angle measured clockwise from north, given as a three-digit number.
What does it mean for an object to be in equilibrium?
The forces on it are balanced, resulting in a resultant force of zero.
What should the scale diagram of forces in equilibrium form?
A triangle.
How can you find a missing force when an object is in equilibrium?
Draw the known forces to scale and tip-to-tail, then join the end of the last force to the start of the first force.
True or False: A resultant force is zero if the tip of the last force drawn ends where the tail of the first force begins.
True.
What is required to stretch, compress, or bend an object?
More than one force acting.
What are objects that can be elastically deformed called?
Elastic objects (e.g., a spring).
What occurs when an object has been inelastically deformed?
It doesn’t return to its original shape and length after the force has been removed.
What happens to energy when an object is elastically deformed?
All this energy is transferred to the object’s elastic potential energy store.
What is the relationship between extension and force for a stretched spring?
The extension is directly proportional to the load or force applied.
What is the limit of proportionality?
The maximum force above which the extension is no longer proportional to force.
What happens to the graph of force against extension when the limit of proportionality is exceeded?
The graph curves, indicating that extension is no longer proportional to force.
Fill in the blank: An object that can return to its original shape after deformation is called an _______.
elastic object.
What is displacement?
Displacement is a vector quantity measuring distance and direction in a straight line from the starting point to the finishing point.
Example: ‘The plane flew 5 metres north.’
If you walk 5 m north and then 5 m south, what is your displacement?
0 m
The distance travelled in this case is 10 m.
What is the difference between speed and velocity?
Speed is a scalar that measures how fast you’re going, while velocity is speed in a given direction.
Example: ‘30 mph north’ is velocity.
What is the typical speed of a person walking?
1.5 m/s
What is the typical speed of a person running?
3 m/s
What is the typical speed of a person cycling?
6 m/s
What factors can affect the speed at which a person walks, runs, or cycles?
Fitness, age, distance travelled, terrain, and other factors.
Terrain refers to the type of land being traversed, such as roads or fields.
What is the speed of sound in air?
330 m/s
What factors can affect wind speed?
Temperature, atmospheric pressure, and nearby structures like buildings or forests.
Forests can reduce the speed of air travelling through them.
What is acceleration?
Acceleration is speeding up (or slowing down) at a constant rate.
Acceleration is distinct from velocity or speed.
How is acceleration defined?
Acceleration is the change in velocity in a certain amount of time.
Example: A cat accelerates at 2.5 m/s.
How do you calculate average acceleration?
Average acceleration can be calculated using the formula: a = (change in velocity) ÷ (time).
Example: From 2.0 m/s to 6.0 m/s over 1.6 seconds.
What is deceleration?
Deceleration is negative acceleration that occurs when something slows down.
The change in velocity is negative.
What does uniform acceleration mean?
Uniform acceleration means a constant acceleration.
Acceleration due to gravity (g) is approximately 9.8 m/s².
What is the initial velocity?
Initial velocity is the starting velocity of the object.
Example: A van traveling at 23 m/s.
What can be plotted on a distance-time graph?
The distance travelled by an object moving in a straight line
Distance-time graphs show the relationship between distance and time for an object’s journey.
What does the gradient of a distance-time graph represent?
Speed
The steeper the graph, the faster the object is moving.
What do flat sections on a distance-time graph indicate?
The object is stationary
Flat sections mean the object is not moving.
What does a straight uphill section on a distance-time graph indicate?
Travelling at a steady speed
The distance is increasing consistently over time.
What do curves on a distance-time graph represent?
Acceleration or deceleration
Curved sections indicate changing speeds.
What does a steepening curve on a distance-time graph indicate?
The object is speeding up
An increasing gradient shows acceleration.
How can you find the speed at a curving
point on a distance-time graph?
By finding the gradient of the tangent to the curve at that point
This method helps in determining instantaneous speed.
What does the gradient of a velocity-time graph represent?
Acceleration
Acceleration is defined as change in velocity divided by time.
What do flat sections on a velocity-time graph indicate?
Travelling at a steady speed
The velocity remains constant during these sections.
What do uphill sections on a velocity-time graph indicate?
Acceleration
The velocity is increasing.
What do downhill sections on a velocity-time graph indicate?
Deceleration
The velocity is decreasing.
What does the area under a velocity-time graph represent?
The distance travelled in that time interval
The area can be calculated using geometric shapes or counting squares.
What happens to the acceleration of a falling object as speed increases?
The acceleration gradually decreases as friction builds up.
What is terminal velocity?
The maximum speed an object reaches when the frictional force equals the accelerating force.
What is the relationship between the shape of an object and its terminal velocity?
Typically, the less streamlined an object is, the lower its terminal velocity.
How does surface area affect terminal velocity?
Objects with large surface areas tend to have lower terminal velocities.
Fill in the blank: The _______ force and the frictional force become equal at terminal velocity.
accelerating
What is Newton’s First Law?
A resultant force is needed to make something start moving, speed up, or slow down.
If the resultant force on a stationary object is zero, it remains stationary. If the resultant force on a moving object is zero, it continues moving at the same velocity.
What happens if the resultant force on a moving object is zero?
The object will carry on moving at the same velocity.
This means the same speed and direction.
How is acceleration related to resultant force?
Acceleration is directly proportional to the resultant force acting on an object.
This relationship can be expressed as F ∝ a.
What is the relationship between acceleration and mass?
Acceleration is inversely proportional to the mass of the object.
A larger mass results in less acceleration for a fixed resultant force.
What is inertia?
The tendency for motion to remain unchanged.
Inertia means that objects at rest stay at rest and objects in motion continue in motion unless acted upon by a resultant force.
How is inertial mass defined?
It measures how difficult it is to change the velocity of an object.
Inertial mass can be calculated using F = ma.
What does Newton’s Third Law state?
The forces two objects exert on each other are equal and opposite.
This principle explains interactions between objects.
What is the formula for calculating stopping distance?
Stopping Distance = Thinking Distance + Braking Distance
What factors affect braking distance?
- Your speed
- The weather or road surfaces
- The condition of your tyres
- How good your brakes are
Is momentum a scalar or vector quantity?
Momentum is a vector quantity
This means it has both size and direction.
How does mass affect momentum?
Greater mass results in greater momentum
The same applies for greater velocity.
What is the principle of conservation of momentum?
Momentum Before = Momentum After
In a closed system, the total momentum remains constant before and after an event.
What characterizes a closed system in terms of momentum?
No external forces act
This means total momentum is conserved during events like collisions.
Fill in the blank: Momentum is conserved in a _______.
closed system
This means that total momentum before an event equals total momentum after the event.
