P10 - Forces and Motion Flashcards
What is Newton’s First Law?
If the resultant force acting on an stationary object is zero, then the object will remain still. If the resultant force acting on a moving object is zero, the object will continue moving at a constant speed
What is Newton’s Second Law?
Force = Mass x Acceleration
F = m a
(N) (kg) (m/s²)
What is Newton’s Third Law?
When 2 objects interact, the forces they exert on each other are equal in magnitude and opposite in direction
What is the inertia?
The tendency of an object to stay at rest or to continue at a constant speed
What is the inertial mass?
A measure of how difficult it is to change an object’s velocity
What is the resultant force needed for?
To change an object’s velocity
What does a low inertial mass mean for an object?
That it is easy to change it’s velocity (start moving and slow down)
What does a high inertial mass mean for an object?
That it is hard to change it’s velocity (start moving and slow down)
What is mass?
The measure of physical mass an object is comprised of
What is weight?
The force acting on a mass due to gravity
How do you alter an object’s weight?
By altering the gravitational field strength
What is the equation for weight?
Weight = Mass x gravitational field strength
W = m x g
(N) (kg) (N/kg) or (m/s²)
When you drop an object, why does it fall?
Because of it’s weight. No other forces act on it so the resultant force is the weight. The object accelerates at whatever the measurement of gravity is (9.8N/kg on Earth)
If an object falls in a fluid then…
The fluid drags on the object due to friction between the fluid and surface of the object. The acceleration of the object decreases as it falls because the frictional force increases as the objects speeds up.
What is the thinking distance?
The distance the vehicle goes in the time it takes the driver to apply the brakes after realising they need to stop
What is the braking distance?
The distance the vehicle travels from when the brakes are first applied to when it completely stops
What factors affect thinking distance?
Age
Alcohol
Drugs
Speed
Tiredness
What factors affect braking distance?
Footwear
Type of car
Location of car
Type of road/ surface
Weather
Speed
What is the total stopping distance?
The thinking distance + braking distance
What does an object’s momentum tell us?
How difficult it will be to stop it moving
What is the equation for momentum?
Momentum = Mass x Velocity
P = m x v
(kgm/s) (kg) (m/s)
What is the Law of Conservation of Momentum?
In a closed system, the total momentum of an object is the same before and after collision
What is the equation to find Force from Momentum and Time
Force = Δ Momentum ÷ Δ Time
F = ΔP ÷ Δt
(N) (Kgm/s) (s)
What is the impulse?
A force acting for a length of time
What is the equation for impulse?
Δ Momentum = Force x Δ Time
ΔP = F x ΔT
(Kgm/s) (N) (s)
What is Hooke’s Law?
The extension of an object is directly proportional to the force that is applied to it provided that the limit of proportionality is not exceeded
What happens to an object if its limit of proportionality is exceeded?
The object will snap/break
What is the equation associated with Hooke’s Law?
Force = Spring Constant x Extension
F = k x e
(N) (N/m) (m)
What is the practical for Hooke’s Law?
- Attach the spring to the clamp and let it hang freely
- Attach/hold a ruler vertically next to the spring
- Measure length of spring with no force acting on it
- Hang mass on the spring and re-measure the length
- Repeat this with more mass until 6N is hanging from the spring
- Record results in a table
What is the practical for Force and Acceleration?
Experiment 1: Varying force to see how it affects acceleration
* Make ramp for trolley to go down
* Have a pulley clamped to the desk so the trolley can go down the ramp
* Have a lightgate clamped to a stand to record the trolley’s speed
* Add a certain mass to the pulley and record initial speed, final speed and time taken
* From this you can find out the acceleration and the force on the pulley
* Repeat this with different masses on the pulley
Experiment 2: Varying mass to see how it affects acceleration
* Same as experiment 1, except add the mass to the trolley instead
What are some car safety features?
Crumple Zones, Seatbelts, Airbags, Anti-lock Brakes, and Electronic Collision Avoidance Systems
What is a crumple zone and how does it work?
It’s the area of a vehicle that is designed to crumple if the vehicle crashes, to absorb impact and dissipate the energy away from the driver and passengers
What do seatbelts do?
Designed to keep people in their seats so they don’t get thrown around inside or outside the vehicle if it crashes
What do airbags do?
Protects passengers from hitting the interior of the vehicle or objects outside of the vehicle. If the sensors detect a crash, then the airbags are filled with nitrogen in a fraction of a second
What do anti-lock brakes do?
They prevent skidding by keeping the wheels from locking up during braking to maintain traction with the road surface
What do electronic collision avoidance systems do?
Often found in newer cars, involves sensors to detect pedestrians and objects with accuracy. It alerts and assisters driver to avoid imminent crashes
