P5 - Forces Flashcards
What are scalar quantities?
Only have magnitude
What are the five examples of scalar quantities?
Speed
Distance
Temperature
Mass
Time
What are vector quantities?
Have magnitude and a direction
What are the five examples of vector quantities?
Force
Velocity
Displacement
Acceleration
Momentum
What is the definition of a force?
A push or a pull on an object caused by it interacting with something.
What is the difference between a contact and non - contact force?
Contact has to be touching, non- contact does not.
What are three examples of a contact force?
Friction
Tension
Air resistance
What are three examples of a non - contact forces?
Electrostatic force
Gravitational force
Magnetic force
What is the definition of weight?
The force that acts on an object due to gravity.
What is the definition of equilibrium?
When’s the forces acting on an object are balanced and the resultant force is zero.
What is the definition of resultant force?
A single force of hay can replace all the forces acting on an object to give the same effect as all original forces acting together.
When is work done done on an object?
When a force moves on an object from one point to another, energy is transferred and work is done on the object.
What has to be done to change the shape of a spring?
More than one force has to act on a stationary object to change its shape.
What is the extension of a stretched spring directly proportional to?
The load or force applied
What happens when the force gets too big?
The extension is no longer proportional to the force.
What are the typical speeds for walking, running, cycling, a car, a train, a plane and sound?
1.5m/s
3m/s
6m/s
25m/s
30m/s
250m/s
330m/s
What is the definition of acceleration?
Change in velocity in a certain time
What is the definition of friction?
A force that acts to oppose an objects motion. It always acts in the opposite direction to movement.
What is the definition of a drag?
The frictional force caused by any fluid on a moving object.
What are three factors affecting reaction times?
Tiredness
Drugs
Alcohol
What is the ruler drop test?
- Get someone to hold ruler so zero is between thumb and forefinger
- Ruler gets dropped without warning. Catch it as quickly as possible.
- Use distance ruler fell to calculate the reaction time.
What does it mean the longer the distance?
The longer the reaction time
What is the thinking distance?
How far the vehicle moves during driver’s reaction time
What is the braking distance?
The distance taken to stop whilst brakes are applied
What 2 factors can increase thinking distance?
- Faster vehicle speed
- Slow driver reaction times
What 4 factors increase braking?
- Faster vehicle speed
- Wet and icy weather
- Poor road surface
- Damaged or worn brakes or tyres
What work done is done when stopping?
- Driver brakes, causing brake pads to be pressed onto wheels
- Friction between them causes work to be done
- Energy transferred from kinetic energy stored of wheels to thermal energy stores of brakes
- Brakes, heat up
What does it mean the bigger the stopping distance?
More space drivers need to leave between their car and one in front
What if speed doubles?
Thinking distance doubles and braking distance quadruples.
What is the conservation of momentum?
In a closed system, the total momentum before an event (eg collision) equals total momentum after an event.
What are five safety features that increase time for change in momentum?
Air bags
Seat belts
Cushioned playground flooring
Crash mats
Bike helmets
How do air bags increase time for change in momentum?
- Inflates during car wash
- Compressing air decreases velocity over a longer time compared to hitting dashboard
- Rate of change of momentum = smaller
- Forces felt are smaller so less severe injuries
