Forces And Motion Flashcards
What is speed defined as?
The distance travelled per unit time
Speed is a scalar quantity.
What does it mean if the speed of something is changing?
It is accelerating or decelerating
Acceleration is a change in speed over time.
What is the formula for average speed?
average speed = total distance / total time
This formula calculates the mean speed over a specific distance.
What is velocity?
The speed in a given direction
Velocity is a vector quantity.
What is acceleration?
The change in velocity per unit time
Acceleration can be positive (speeding up) or negative (slowing down).
What is the formula for acceleration?
acceleration = change in velocity / time
It can also be expressed as a = (final speed - initial speed) / time.
What is the equation relating final speed, initial speed, acceleration, and distance?
(final speed)² = (initial speed)² + (2 × acceleration × distance)
This equation is useful in kinematic calculations.
In which units is distance measured?
Metres (m)
Distance is a scalar quantity.
In which units is time measured?
Seconds (s)
Time is a scalar quantity.
In which units is speed and velocity measured?
Metres per second (m/s)
Both are scalar and vector quantities, respectively.
In which units is acceleration measured?
Metres per second squared (m/s²)
Acceleration indicates how quickly velocity changes.
What does a gradient represent in a displacement-time graph?
Velocity
The steepness of the gradient indicates the speed of the object.
What does a negative gradient in a displacement-time graph indicate?
Returning back to the starting point
This indicates a change in direction.
What does a horizontal line in a displacement-time graph mean?
It is stationary
No displacement means no movement.
What does a curved line in a displacement-time graph indicate?
The velocity is changing (accelerating/decelerating)
The curvature reflects a non-constant speed.
What does the gradient represent in a velocity-time graph?
Acceleration
The steeper the gradient, the greater the acceleration.
What does a negative gradient in a velocity-time graph indicate?
Deceleration
This shows a reduction in speed over time.
What does a horizontal line in a velocity-time graph mean?
Constant speed
The object travels at the same speed throughout the time interval.
What does the area under the line in a velocity-time graph represent?
The distance travelled
This is useful for calculating total distance from speed over time.
What does a curved line in a velocity-time graph indicate?
The acceleration is changing
The curvature reflects a non-constant acceleration.
Fill in the blank: If the speed is zero, it is _______.
at rest
This indicates no movement.
What is the difference between a vector and a scalar?
A vector has magnitude and direction; a scalar has just a magnitude.
Give examples of scalars.
- Distance
- Speed
- Time
- Energy
Give examples of vectors.
- Displacement
- Velocity
- Acceleration
- Force
What can forces change in a body?
Forces can change the speed, shape or direction of a body.
In what unit are forces measured?
Newtons (N)
What is friction?
Friction is a force between two surfaces which impedes motion and results in heating.
What is air resistance?
Air resistance is a form of friction.
How do you find the resultant of two or more forces acting along the same line?
Add them together if in the same direction and subtract if in the opposite direction.
State Newton’s first law.
An object has a constant velocity unless acted on by a resultant force.
State Newton’s second law.
Force = mass X acceleration (F = ma).
What is mass?
Mass is a measure of how much matter is in an object, measured in kilograms (kg).
What is weight?
Weight is a gravitational force, the effect of a gravitational field on a mass.
What is the equation for weight?
weight = mass X gravitational field strength.
What is the gravitational field strength on Earth?
10 N/kg.
How do you calculate weight using gravitational field strength?
W = mg.
What happens to a body falling in a uniform gravitational field initially?
Initially, there is no air resistance and the only force acting on it is weight.
What occurs as a body falls in a gravitational field?
It accelerates, increasing its speed and hence air resistance.
What happens to the resultant force as a body accelerates in a gravitational field?
The resultant force downwards decreases.
What happens when the air resistance equals the weight of the falling body?
There is no resultant force, so there is no acceleration and terminal velocity is reached.
What is the force applied to a spring called in Hooke’s law?
F
F represents the force applied to the spring.
What does ‘k’ represent in Hooke’s law?
Spring constant
‘k’ is a measure of the stiffness of the spring.
What is the distance travelled before a driver applies the brakes called?
Thinking distance
Thinking distance increases with greater speed and slower reaction times.
What factors can increase thinking distance?
- Greater speed
- Slower reaction time due to alcohol, tiredness, or distractions
- Caffeine reduces thinking distance
Caffeine affects reaction time positively.
What is the distance travelled from pressing the brakes to the vehicle stopping called?
Braking distance
Braking distance can be affected by speed, mass, and road conditions.
What factors can increase braking distance?
- Greater speed or mass
- Poor road conditions (icy, wet)
- Car conditions (worn tires, worn brake pads)
These factors can significantly affect stopping performance.
What is the formula for calculating the stopping distance?
Stopping distance = Thinking distance + Braking distance
This represents the total distance a vehicle travels before coming to a stop.
What is deformation in the context of forces?
Change in size and shape of a body
Deformation can be elastic or plastic depending on the material’s response to the applied force.
What is elastic deformation?
Object returns to its original shape when load is removed
An example is a spring being stretched under normal usage.
What is the limit of proportionality?
Point where the force-extension graph stops being linear
Beyond this point, the material does not obey Hooke’s law.
What does the gradient of the force-extension graph represent?
Spring constant, k
The steeper the gradient, the stiffer the spring.
True or False: A non-linear force-extension graph indicates deformation that follows Hooke’s law.
False
Non-linear graphs indicate deformation that does not follow Hooke’s law.
What occurs in the plastic region of a force-extension graph?
Permanent deformation occurs
After this region, the material will likely fracture.
What is the relationship defined by Hooke’s law?
F = kx
This relationship describes how the force applied to a spring relates to its extension.
Hookes law definition
if you apply a force to a spring, then the force stretches spring. And if you don’t stretch too much, Hooke’s law says that the amount of force you apply is proportional to the stretch. So, that means that if you apply twice the force, you get twice the stretch.
Scalar quantity
Only have a magnitude (size)
Vector quantity
Have direction and magnitude
Vector quantity
Have direction and magnitude
