P6 Flashcards
Examples of scalar quantities?
mass
speed
distance
time
temperature
What is the difference between scalar and vector quantities?
A scalar quantity has only magnitude (size) but no direction. Vector quantity has both magnitude and direction. (west, east)
Examples of vector quantities?
weight
force
acceleration
displacement
Example of scalar and vector quantity?
in a journey, we have travelled a DISTANCE of 800m (scalar) but our displacement is 500m west from our start point
How is force a vector quantity?
because they have a magnitude and a direction
Example of normal contact force?
a lamp on a table. the lamp is exerting a downward force onto the table (weight), however, the table is exerting an upward force on the lamp
Weight (N) =?
mass X gravitational field strength
What is the single point called that acts on an object?
centre of mass
How to calculate resultant force?
larger force - smaller force
What is a freebody diagram to show the forces acting on an object?
the object is shown as a point.
the forces are show as arrows starting at the point, and shows us the direction
the length of the arrows show the size of the force
lift meaning?
for example an aeroplane, there must be a force which is the same magnitude as the plane acting in the opposite direction, so it can remain at a constant altitude
thrust meaning?
a forward force
e.g. engines on a plane
go over vector diagrams
Work done?
a measure of energy transferred
What’s the key fact about elastic materials?
they will always return to their original length or shape if we take away the forces acting on them
e.g. slinky, rubber bands/gloves
Elastic deformation?
temporary change in the form of an object due to an applied stress, which reverts to its original shape once the stress is removed
What has to happen in order to change an objects length or shape?
have to apply more than one force
Key fact about inelastic forces?
when we stretch them, they do not return to their original length when the force is removed
e.g. polymers
Force=?
spring constant x compression
What is work done equal to when an object is stretched?
elastic potential energy only if the object is not inelastically deformed
Displacement?
the distance that an object moves in a straight line from start to finish
e.g. 500m north
typical normal walking speed and running speed?
1.5m/s
3m/s
average speed for a
car on main road?
fast train in uk?
plane?
13m/s
50m/s
250m/s
Does sound travel faster on warmer or cooler days?
warmer days
Velocity?
A objects speed in a given direction
e.g. 20m/s south
What happens if an object moves at a constant speed in a circle?
its velocity is constantly changing
Terminal velocity?
when the force of air resistance balances the force due to gravity, so the object stops accelerating and moves at a constant velocity e.g. skydiving
What do all of Newton’s laws of motion talk about?
describe the effects that forces have on the motion of an object
Newton’s first law of motion
If the resultant force acting on stationary object is zero, then the object will remain stationary (also moving objects stay the same) e.g. If a car is stationary or moving and has a force of 50 N to the left and right, it will remain a constant speed
Newtons second law of motion?
The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object
force=?
mass x acceleration
how many newtons does a typical family car require to accelerate from a main road to a motorway?
2000 N
Inertia?
Objects will stay still or keep the same motion, unless you apply a resultant force
inertial mass?
a measure of how difficult it is to change the velocity of an object
what will an object with a large inertial mass require?
A larger force to produce a given acceleration
Newton’s third law of motion?
whenever two object interact, the forces they exert on each other are equal an opposite
stopping distance?
The total distance travelled from when the driver first spots and obstruction to when the car stops
thinking distance
The distance travelled by the car during the drivers reaction time
Braking distance?
The distance, the car travels from when the driver applies the brakes to when the car stops
The greater the speed of the vehicle…?
the greater the stopping distance
what two things can make reaction time longer?
Alcohol
Drugs
two things that affect the braking distance?
wet, icy conditions
worn tyres/brakes
kinetic energy=?
1/2 mass x (velocity)2
how much momentum do objects that are not moving?
No momentum
momentum=?
mass x velocity
conservation of momentum?
in a close system, the total momentum before an event is equal to the total momentum after an event e.g. Van crashes into a car and they both move slower but the momentum is the same because the mass is added together of both vehicles
