Forces and motion Flashcards
Mass: ?
Distance: ?
Speed: ?
Acceleration: ?
Force: ?
Time: ?
Gravity: ?
Mass: kilogram (kg)
Distance: metre (m)
Speed: metre per second (m/s)
Acceleration: metre per second squared (m/s^2)
Force: newton (N)
Time: second (s)
Gravity: newton/kilogram (N/kg)
What is on the y and x axis on a d/t graph?
A distance time graph has distance on the y axis (usually in metres) and time on the x axis (usually in seconds)
Which property of the d-t graph can be used to calculate speed? How do you calculate it?
The gradient of the line
calculation: change in y/ change in x
What does it mean if the line is stationary on a d/t graph?
If the line is flat then the object is stationary.
What is the relationship between average speed, distance moved and time taken?
speed (m/s) = distance travelled (m)/ time taken (s)
What is the relationship between acceleration, change in velocity and time taken?
Acceleration = ((final velocity) - (initial velocity))/time = change in velocity/time
What is on the y and x axis on a v-t graph?
on a velocity time graphthe velocity is on the y axis (usually in m/s) and time is on the x axis (usually in s).
What does it mean if the line is flat on a v-t graph?
If the line is flat then the object is moving at a constant velocity.
How do you find the acceleration of a v-t graph? what is the calculation?
The gradient of the line
calculation: acceleration= change in y/ change in x = change in velocity/time
How do you find the total distance traveled using a v-t graph?
The area under the graph can be calculated as rectangles and triangles, or by counting boxes, is equal to the distance travelled.
What is the relationship between final speed, initial speed, acceleration, and distance moved? What is v, u, a and s?
v= final speed
u= initial speed
a= acceleration
s= distance moved
v2=u2+2as
(final speed)2 = (initial speed)2 + (2 × acceleration × distance moved)
In what ways can forces affect bodies?
force can cause an object to:
*speed up
*slow down
*change direction
*change shape (stretch, compress, or deform)
What is tension?
an object that is being stretched will experience a tension force.
What is applied force?
A force that is exerted on something by something else
What is spring force?
A force that is exerted when a spring is squashed or stretched.
What is drag force?
Force that is exerted on an object as it moves through a liquid or gas, also know as air resistance.
What is frictional force?
A force that is exerted on an object in the opposite direction to weight
What is normal force?
A force that is exerted on an object in the opposite direction to weight.
What is magnetic force?
A force that is exerted on an object that is magnetic (either repulsion or attraction)
what is electric force?
A force that is exerted on an object that is charged (either positive or negative)
What is gravitational force?
Force that is exerted on all objects with mass
What is weight?
downwards force due to gravity
What is upthrust?
upward force that a liquid or gas exerts on a body floating in it
What is lift?
force that uses motion to make an object rise up
What are scalar and vector quantities?
scalars are quantities with only magnitude (size)
vectors are quantities with magnitude (size) and direction
Is force a vector or scalar quantity?
Force has a magnitude measured in (N) but it also has a direction, a push or a pull, up, down, left or right. So force is a vector.
How do you calculate resultant force?
Forces along a line can combine by addition.
What does it mean if the forces on both sides of the object are equal?
- The object is either still or moving at a constant speed
- there is no resultant force
- the object doesn’t accelerate or decelerate
WHat happens if there is a resultant force?
the objects accelerates or decelerates
What is friction and what force does it oppose?
Friction is caused by surfaces rubbing. The force always acts in the opposite direction to motion.
what is the relationship between unbalanced force, mass and acceleration?
Force = Mass x Acceleration.
What is the relationship between weight, mass and gravitational field strength?
Weight (N)= Mass (kg) x gravitational field strength (N/kg)
What is the gravitational field strength on earth?
gravitational field strength on earth is approx. 10 N/kg and in GCSEs is taken to be 10 N/kg.
How do you calculate stopping distance?
Stopping distance = Thinking distance + Breaking distance
describe the factors affecting the thinking distance:
Thinking distance Affected by:
- Tiredness
- Alcohol
- speed of the car
- Drugs (avoid as drugs can increase or decrease thinking distance)
describe the factors affecting the braking distance:
Braking distance affected by:
- Road conditions
- Tyre conditions
- Brake conditions
- speed of the car
- mass of the car
describe the forces acting on falling objects (explain why falling objects reach a terminal velocity)
Initially the only force is weight as drag is proportional to velocity. So the object accelerates downwards. As it accelerates the velocity so the drag increases as well. meaning there is a smaller resultant force downwards so a smaller acceleration. Until the object reaches a speed where the drag is equal to the weight meaning there is no acceleration, this velocity is know as terminal velocity.
What is Hooke’s law?
Hooke’s law is that extension is directly proportional to force applied. This is shown by the straight line on the force-extension graph. Hooke’s law is obeyed as long as the line is straight.
What is elastic behavior? What is elastic limit?
An object that can be described as having elastic behavior is an object that when it is pulled or stretched, it doesn’t break, so when the forces are removed, it will return to its original state, in a spring this occurs when the force is lower than the elastic limit.
Elastic Limit
When the material is stretched too far and loses its elasticity and reached its elastic limit. It is unable to return to its original shape.
What are the 2 forces falling object experience?
- weight (due to gravity)
- air resistance (due to friction)
Explain what happens to the air resistance and weight on an object as it falls:
- Initially, the upwards air resistance is very small because the skydiver isn’t falling very quickly - an unbalanced force object will accelerate downwards (there is a resultant force)
- As the skydiver speeds up, the air resistance increases eventually growing large enough to balance the downward weight force - no more resultant force and there is no acceleration so the object is traveling at a constant speed (which is known as terminal velocity)
What does hookes law state?
The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality. Directly proportional means that as more force is applied, the greater the extension (and vice versa)
What is the limit of proportionality?
The limit of proportionality is where if more force is added, the object may extend but will not return to its original shape when the force is removed (it will be inelastically deformed)
- This limit varies according to the material
What is the relationship between force and extension called according to Hooke’s law?
Hooke’s law is the linear relationship between force and extension:
- This is represented by a straight line on a force-extension graph
Examples of materials that undergo elastic deformation are:
Rubber bands
Fabrics
Steel springs
Examples of materials that undergo inelastic deformation are:
Plastic
Clay
Glass
