Topic 2 Flashcards
Motion
What is the definition of speed?
Speed is defined as distance travelled per unit time.
Is speed a scalar or vector quantity?
Speed is a scalar quantity.
What does a scalar quantity contain?
A scalar quantity contains only a magnitude (without a direction).
What is the equation for calculating speed?
The equation for calculating speed is: v = s / t
Where: v = speed (m/s), s = distance travelled (m), t = time (s).
What is average speed?
Average speed is the total distance travelled divided by the total time taken.
How do you calculate average speed?
The equation for calculating average speed is: average speed = distance travelled / time taken.
What is an example of average speeds?
A hiker might have an average speed of 2.0 m/s, whereas a bumble bee can have average speeds of up to 4.5 m/s.
What is a formula triangle used for?
A formula triangle is used for knowing how to rearrange physics equations.
How do you use a formula triangle?
To use a formula triangle, cover up the quantity to be calculated and observe the positions of the other two quantities.
What is the typical average speed of planes?
Planes fly at typical average speeds of around 250 m/s.
How do you calculate distance travelled using average speed?
Distance travelled = average speed × time taken.
How do you convert hours to seconds?
To convert hours to seconds, multiply by 3600 (2 hours = 2 × 60 × 60 = 7200 s).
What is velocity?
Velocity is a vector quantity with magnitude and direction.
How is velocity defined?
Velocity is defined as speed in a given direction.
How can direction of velocity be expressed?
The direction of velocity can be given in words or using positive or negative values.
What is the equation for velocity?
The equation for velocity is: v = s / t
Where: v = velocity (m/s), s = displacement (m), t = time (s).
What is the difference between speed and velocity?
Speed is a scalar quantity, while velocity is a vector quantity.
What is acceleration?
Acceleration describes how the velocity of an object changes over time.
How is acceleration defined?
The rate of change of velocity.
What is the formula for acceleration?
a = increment v / increment t
Where: a = acceleration (m/s²), increment v = change in velocity (m/s), increment t = time taken (s).
What does the change in velocity represent?
The difference between the initial and final velocity.
What is the formula for change in velocity?
increment v = v - u
Where: increment v = change in velocity (m/s), v = final velocity (m/s), u = initial velocity (m/s).
What are the ways an object can change its velocity?
Speeding up, slowing down, changing direction.
What is positive acceleration?
When an object speeds up.
What is negative acceleration?
When an object slows down.
What does a negative acceleration value indicate?
The object is slowing down.
What are the units for acceleration?
Metres per second squared (m/s²).
How do you calculate change in velocity?
Subtract the initial velocity from the final velocity.
Worked Example: What is the change in velocity of a train that decelerates from 50 m/s to 42 m/s?
increment v = 42 - 50 = -8 m/s.
Worked Example: What is the deceleration of the train over 30 seconds?
a = increment v / increment t = -8 / 30 = -0.27 m/s².
What is a distance-time graph used for?
A distance-time graph is used to describe the motion of an object and calculate its speed.
What does a straight line on a distance-time graph indicate?
A straight line indicates that an object is moving at a constant speed.
What does a horizontal line on a distance-time graph represent?
A horizontal line indicates that the constant speed is zero, meaning the object is stationary.
What does a gradient on a distance-time graph represent?
The gradient represents the magnitude of the object’s velocity, or its speed.
What does a steeper slope on a distance-time graph indicate?
A steeper slope represents a greater speed.
What does a shallower slope on a distance-time graph indicate?
A shallower slope represents a slower speed.
What does a curved line on a distance-time graph indicate?
A curved line indicates that the speed of the object is changing, meaning the object is accelerating.
What does an increasing gradient on a distance-time graph indicate?
An increasing gradient indicates that the speed is increasing over time.
What does a decreasing gradient on a distance-time graph indicate?
A decreasing gradient indicates that the speed is decreasing over time.
How can the speed of a moving object be calculated from a distance-time graph?
Speed can be calculated from the gradient of the line on a distance-time graph using the formula: speed = gradient = Δy / Δx.
What are the steps to calculate the speed of a train from a distance-time graph?
- Draw a large gradient triangle on the graph. 2. Convert units for distance and time into standard units. 3. State that speed is equal to the gradient of a distance-time graph. 4. Substitute values to calculate the speed.
What is the formula for speed in relation to distance and time?
The formula is v = s / t, where v is speed, s is distance, and t is time.
What is a speed-time graph used for?
A speed-time graph is used to describe the speed of an object and calculate its acceleration.
What does a straight line on a speed-time graph indicate?
If an object is moving at a constant acceleration, the speed-time graph will be a straight line.
What does a horizontal line on a speed-time graph indicate?
If the constant acceleration is zero, the line will be horizontal.
What does a line with a gradient on a speed-time graph indicate?
If the constant speed is non-zero, the line will have a gradient.
What does it mean if an object has an acceleration of zero?
If an object has an acceleration of zero, the object is travelling at a constant velocity.
What does it mean if the constant speed is zero?
If the constant speed is zero, then the object is stationary.
What does the gradient of a speed-time graph represent?
The gradient of a speed-time graph represents the object’s acceleration.
What does a steeper slope on a speed-time graph indicate?
A steeper slope, or a higher gradient, represents a greater acceleration.
What does a shallower slope on a speed-time graph indicate?
A shallower slope, or a lower gradient, represents a slower acceleration.
What does a positive gradient on a speed-time graph indicate?
A positive gradient represents an increasing speed, or acceleration.
What does a negative gradient on a speed-time graph indicate?
A negative gradient represents a decreasing speed, or deceleration.
How can speed-time graphs be used in CIE IGCSE Physics?
You may be asked to plot a graph of your own, or to interpret information given to you in a graph.
What does the area under a speed-time graph represent?
The area under a speed-time graph represents the distance travelled.
How do you calculate the area of a triangle on a speed-time graph?
The area can be calculated using: A_T = 1/2 b h.
How do you calculate the area of a rectangle on a speed-time graph?
The area can be determined using: A_R = b h.
What is the formula for the total distance travelled using a speed-time graph?
The total distance travelled can be determined by finding the total area under the speed-time graph.
How can you determine the distance travelled for part of the journey on a speed-time graph?
The distance travelled for part of the journey can be determined by finding the area under the graph for a specific time interval.
What can the shape of a speed-time graph show?
The shape of the graph can show constant acceleration or changing acceleration.
What does the gradient of a speed-time graph indicate?
The gradient shows the acceleration of a moving object.
What does a positive gradient on a speed-time graph indicate?
A positive gradient indicates that the object is accelerating (speed increases with time).
What does a negative gradient on a speed-time graph indicate?
A negative gradient indicates that the object is decelerating (speed decreases with time).
What does a straight line on a speed-time graph represent?
A straight line represents constant positive acceleration, where velocity increases at a constant rate.
What characterizes increasing positive acceleration on a speed-time graph?
The graph is a curve, and velocity increases at an increasing rate.
What characterizes decreasing positive acceleration on a speed-time graph?
The graph is a curve, and velocity increases at a decreasing rate.
What characterizes decreasing negative acceleration on a speed-time graph?
The graph is a curve, and velocity decreases at a decreasing rate.
What is a key skill required in CIE IGCSE Physics?
Interpreting graphs is a required skill.
How can acceleration be calculated from a speed-time graph?
Acceleration can be calculated from the gradient of the speed-time graph.
How is the gradient of a straight line on a speed-time graph calculated?
The gradient is calculated using the formula: a = Δv / Δt.
How is the gradient of a curve on a speed-time graph determined?
The gradient at a point on a curve can be found by drawing a tangent to the curve.
What does the gradient of the tangent to a curve represent?
The gradient of the tangent represents the instantaneous acceleration of the object at that moment.
What is the acceleration of free fall?
In the absence of air resistance, all objects fall with the same acceleration regardless of their mass, called the acceleration of free fall.
This is also referred to as acceleration due to gravity.
What is the value of acceleration due to gravity?
The acceleration due to gravity (g) is approximately 9.8 m/s² near Earth’s surface.
How does the velocity of a falling object change over time?
For every second an object falls, its velocity will increase by 9.8 m/s.
What does the symbol ‘g’ represent?
The symbol ‘g’ stands for the gravitational field strength and can be used to calculate the force of weight acting on an object using its mass.
What is the formula for weight?
W = mg, where W is the force of weight (N), m is mass (kg), and g is gravitational field strength (N/kg).
What happens to falling objects in a vacuum?
In a vacuum, there is no air resistance, so the only force acting on falling objects is weight.
This means that all objects fall with the same acceleration.
What is Newton’s second law of motion?
Newton’s second law of motion states that acceleration (a) is equal to the force (F) exerted on an object divided by its mass (m): a = F/m.
What is the relationship between weight and acceleration in a vacuum?
In a vacuum, since the only force acting is weight, acceleration can be expressed as a = W/m, which simplifies to a = g.
What experiment demonstrated that objects fall at the same rate in a vacuum?
Astronauts on the Moon dropped a hammer and a feather from equal heights, and they fell with the same acceleration and landed at the same time.
What is terminal velocity?
Terminal velocity is reached when the force of air resistance equals the force of weight, resulting in no acceleration.
How does a skydiver reach terminal velocity?
Initially, the only force acting on a skydiver is weight, causing acceleration. As speed increases, air resistance increases until it balances with weight, resulting in terminal velocity.
What happens when a parachute is deployed?
Deploying a parachute increases the surface area, greatly increasing air resistance, which then exceeds the force of weight, causing the skydiver to decelerate.
What occurs after a skydiver decelerates post-parachute deployment?
As the skydiver decelerates, air resistance decreases until it equals the weight again, resulting in a new, slower terminal velocity.
