P10 - Forces and Motion Flashcards
Newton’s 2nd law - the acceleration of an object is:
- Directly proportional to the resultant force of an object
- Inversely proportional to the mass of an object
What is an equation for force?
Force = mass x acceleration
What is the unit for force?
Newton
What is the unit for mass?
Kilograms - Kg
What is the unit for acceleration ?
Meters per second squared
What does inertia mean?
The tendency for an object to stay at rest or to continue in uniform motion(constant velocity) is called inertia.
What does inertial mass refer to?
This refers to the measure of difficulty in changing an object’s velocity
What does inertial mass mean?
An object with more mass has a greater tendency to resist a change in its moving state. More force is required to move a greater mass from rest.
What is weight measured in ?
Newton
What is the formula for weight?
Weight = mass x acceleration (due to gravity) W = mg
What does terminal velocity mean?
The maximum velocity that an object can travel at in a fluid - liquid(water) and gas(air).
What is stopping distance?
The distance it takes for a vehicle to stop. (Total stopping distance) = thinking distance + braking distance
What is thinking distance?
The distance travelled in between the driver realising he needs to brake and actually braking / The distance travelled during the reaction time.
What are factors affecting thinking distance? Give (3).
- How fast the car is going
- How intoxicated the person is(drinking/drugs)
- Concentration of the person (tiredness)
- Poor visability
What are factors affecting breaking distance? Give (3)
- The speed of the vehicle.
- The mass of the vehicle.
- The condition of the brakes.
- The condition of the tyres(tread).
- The condition of the road( weather)
What is the formula to calculate the breaking force?
a= v^2 - u^2 / 2s.
How do you calculate momentum?
p (momentum)= m(mass) x v(velocity)
What is meant by a closed system?
A physical system that does not exchange matter or energy with its surroundings.
What is an elastic object?
An elastic object is one which regains its shape when the forces deforming it (e.g stretching or squashing) are removed.
What happens when an elastic object is deformed?
When an elastic object is deformed the energy which caused it to deform is stored as elastic energy , whicn is released when the force is removed.
What is compression?
When a force is exerted on an object.
What is tension?
This happens when a force pulls on the object.
What is Hook’s law?
The extension of a spring is directly proportional to the force applied, provided its limit of proportionality is not exceeded.
What happens is a spring passes its limit of propotionality?
The material starts to behave in a non-linear way.
The material will no longer continue to deform and be able to regain its original shape.
Give (3) features designed to reduce the impact felt.
Crumple zone
Air bags
Seat belt
What is the equation for changing the momentum?
Force x time = Change in momentum
What is pressure?
Pressure is the force per unit area
What is the equation for pressure in liquids?
Pressure in liquids equation : p = p(density kg/m cubed) x h(m) x g(N/kg or m/s^2)
What is the equation for pressure?
Pressure (Pa)= Force (N)/ Area (m squared)
