Forces and Motion Flashcards
sped and acceleration, forces and motion
What the equation relating velocity, displacement and time
velocity = displacement/time
What is the equation relating speed distance and time
Speed = distance/time
What is the equation for acceleration
a=v-u/t
In the acceleration equation what do v and u represent
v= final velocity
u = start velocity
In a distance time graph how do you find the velocity
gradient of the line
In a distance time graph what does a flat section represent
Stopped
In a distance time graph what does a straight line at an angle represent
constant velocity
In a distance time graph what does a curve represent
acceleration
In a distance time graph what does a curve that is levelling off represent
deceleration
In a velocity time graph what does a line going uphill represent
acceleration
In a velocity time graph what does a flat line represent
steady speed
In a velocity time graph what does a curve represent
change in acceleration
In a velocity time graph what does a line going down hill represent
deceleration
How would you calculate the distance travelled in a distance time graph
the area under the graph
In a velocity time graph what does the gradient equal
acceleration
What is the equation for acceleration when final velocity is the subject
V= u+at
What is a vector
It has size and direction
What is a scalar
It only has size
Explain what happens when someone jumps out of a plane in terms of terminal velocity
- When the person first jumps there weight is larger then drag so there is a resultant force - so they are accelerating downwards
- As the speed increases so does the drag and eventually they are equal. This means there is no acceleration, no resultant force and they are travelling at a constant velocity (they have reached terminalvelocity)
- When parachute is pulled there is more drag so there is a resultant force upwards so they decelerate until forces are equal and reach terminal velocity again
What are the 2 equations that concern Newtons 2nd law
W=mg
F=ma
In the equation F=ma what does each letter stand for
F= resultant force
m=mass
a= acceleration
W=mg - what is the value of g
10m/s2
What do resultant forces cause
They cause an object to accelerate or decelerate
What happens if there is no resultant force
On object will stay still or if they are already moving they will move at a constant velocity
What is a force and what are there effects
A force is a push or a pull
Forces make a body: change speed, change shape or change direction
Name 4 types of forces
- Friction
- Upthrust
- weight/ gravitational force
- drag/ air resistance
What is the equation for work done
work done = force x distance
What is thinking distance
The distance a car travels whilst the driver reacts to the incident
What is braking distance
It is the distance a car travels once the brakes have been applied until the car is stationary
What is stopping distance
braking distance added to the thinking distance
What affects thinking distance
- speed
- distractions
- fatigue
- alcohol or drug intake
What affects braking distance
- speed
- mass of the car
- road surface
- if the road is wet or icy
- quality of the tyres and brakes
How does speed affect the braking distance
work done by brakes = the kinetic energy transferred
Fxs= mv2/2
so s depends on v2
(assume F and m are constant
What is the relationship between speed and thinking distance
They are directly proportional
What is newtons first law
A body stays at rest or moves with a constant velocity unless a resultant force acts upon it
Newtons third law
Every action force has a equal and opposite reaction force
What is the equation relating velocity acceleration and distance
v2 = u2 + 2as
