Topic 2 - Motion and Forces Flashcards
Newton’s first law
What is the difference between a scalar and vector quantity?
Scalar quantities only have magnitude
Vector quantities have both magnitude and direction
Newton’s 1st law
Define a resultant force
The net force acting on an object after all opposing forces are balanced out.
Newton’s 1st law
State Newton’s 1st law
An object will remain at a constant velocity unless acted upon by a resultant force
Newton’s 2nd law
Define mass
A scalar measurement of the amount of substance there is in an object (kg)
Newton’s 2nd law
Define weight
A force due to the pull of gravity on an object (N)
Vector quantity
Newton’s 2nd law
State the equation for weight
weight = mass * gravity
Mass (kg)
Gravity (N/kg)
Weight (N)
Newton’s 2nd law
State Newton’s second law
Acceleration in the direction of a resultant force depends on:
1. Magnitude of force
2. Mass of object
Force = mass * acceleration
Newton’s 3rd law
State Newton’s 3rd law
For every action there is an equal and opposite reaction
Newton’s 3rd law
What are action reaction forces?
Are a pair of forces on interacting objects, of the same size and in opposite directions always acting on different objects.
Reaction time
How do you measure human reaction time?
- Have them hold a ruler while you have your hand at 0cm
- The person should drop the ruler without telling you when and record at which length you caught the ruler.
- Then use the formula v² - u² = 2as to calculate the final velocity (v)
- Then use a = (v-u) / t in order to calculate the time
v = final velocity (m/s)
u = initial velocity (m/s)
t = time (s)
a = acceleration (m/s²)(9.81 in earth)
s = displacement (m)
Stopping distance
How to calculate stopping distance
Thinking distance + braking distance
Stopping distance
State variables that impact the stopping distance of a vehicle
- Mass of vehicle
- Driver’s reaction time
- Conditions of road
- Speed of vehicle
- Conditions of vehicle’s brakes
- Friction between road and tire
Reaction time
State the variables that could impact a driver’s reaction time
- Distractions
- Alcohol
- Drugs
- Tiredness
Braking distance
What happens to braking distance when speed doubles
Braking distance quadruples (*4)
Rotational forces
What is the formula for calculating moments?
moment (Nm) = force (N) * distance (m)
Distance-time graphs
How do you calculate the speed of a distance-time graph?
Calculate the gradient = change in vertical height / change in horizontal
Distance-time graphs
How do you calculate the average speed of a distance-time graph?
Average speed = total distance / total time
P-Waves
Define P-Waves and state their characteristics
P-waves are a type of seismic waves.
- They are longitudinal meaning they can travel through liquids, solids and gases.
- They are faster than S-Waves
- Refracted in solid mantle to liquid outer core so there are shadow zones (areas where p-waves do not reach due to refraction)
Rotational forces
What is the definition of a moment?
The turning effect of a force
Rotational forces
What is the term for the clockwise and anti-clockwise moments balancing each other out?
Equilibrium
Rotational forces
What does a moment turn around?
A pivot
S-Waves
Define S-Waves and state their characteristics
S-waves are a type of seismic waves.
- They are transverse meaning they can only travel through solids.
- They are slower than P-Waves
- Refracted when travelling through the earth
- Cannot travel through the liquid core crerating large shadow zones (areas where the waves do not reach)
- Infrasound (below 20Hz therefore we cannot hear them)
