Forces Flashcards
What happens to the energy in a car when it slows down?
When a car slows down, energy is transferred from the kinetic energy store of the car to the thermal energy store of the brake pads and brake discs.
Friction between the car’s brake pads and brake discs does mechanical work to oppose the car’s motion.
The work done by the force of friction, given by the equation Work = force x distance
This mechanical work converts the car’s kinetic energy into thermal energy.
As a result, the brake pads and brake discs heat up as energy has been transferred to its thermal energy store.
What are factors affecting thinking distance?
Condition of driver - tiredness, alcohol, drugs, mobile phone, raction time
Speed - faster the car is moving, the further it will go while the driver is reacting
What are the factors affecting braking distance?
Condition of the road (wet, dry etc.)
Condition of the tyres - new, worn (old tyres increase breaking distance
condition of brakes
force exerted by the brakes
mass of the car
speed of car
What is a force?
A push or pull that acts on an object due to the interaction with another object.
What are the two types of forces?
- Contact forces
- Non-contact forces
What are examples of contact forces?
- Friction
- Air resistance
- Tension
- Normal contact force
What are examples of non-contact forces?
- Gravitational force
- Electrostatic force
- Magnetic force
Is force a scalar or vector quantity?
Vector quantity.
Students should be able to describe the interaction between pairs of objects which produce a force on each object. True or False?
True
How should forces be represented?
As vectors.
What is weight? What does weight depend on?
Weight is the force acting on an object due to gravity. The force of gravity close to the earth is due to the gravitational field around the earth.
The weight of an object depends on the gravitational field strength at the point where the object is.
What is the atmosphere?
A thin layer of air around the Earth
How does the density of the atmosphere change with altitude?
It gets less dense with increasing altitude
What creates atmospheric pressure?
Air molecules colliding with a surface
How does the number of air molecules above a surface change with height?
It decreases as the height of the surface increases
What happens to atmospheric pressure as height increases?
It decreases
Fill in the blank: The atmosphere is a _______ layer of air round the Earth.
thin
True or False: Atmospheric pressure increases with altitude.
False
What are the typical values for someone walking, running or cycling?
walking - 1.5m/s
running - 3 m/s
cycling - 6m/s
What does Newton’s 1st law state?
If the forces acting on an object are balanced, the resultant force on the object is 0, then
if the object is stationary, it will remain stationary
and if the object is moving, it will continue to move at a constant velocity
What is inertia?
Inertia is the tendency of object to continure in their state of rest or uniform motion.W
What does Newton’s second law state?
The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
Equation:
force = mass x acceleration
f = ma
What is inertial mass?
nertial mass is a measure of how difficult it is to change thevelocity of an object
inertial mass is defined as the ratio of force over acceleration.
