Lesson 1 Flashcards
What is the formula for density?
P = m/v
What are the units of density?
They can change.
What is density?
Mass per unit volume.
What is the relative density of solid and liquid to gas?
1000 to 1
When will an object float on a substance?
It will float when the substance has a greater average density.
When will an object sink?
An object will sink if it’s average density is greater than the substance it is placed on.
What is a density ladder used for?
A density ladder can be used to show how different substances will float on top of each other due to differing densities.
How do ships float?
Ships float since their average density will be less than that of water.
How are submarines made to sink?
They fill tanks onboard with water.
How do submarines resurface?
They empty tanks and fill them with compressed air.
What is average speed of an object?
It’s the speed measured across the whole journey.
How do you measure average speed?
Measuring the distance travelled (using a metre stick) and the time taken (stopwatch) to travel the whole distance and then using the relationship: v = d/t
What is the speed of an object?
The speed of an object is defined as the distance travelled per second.
What is the instantaneous speed?
Instantaneous speed is the speed at one particular point in the journey.
How can instantaneous speed be found?
Measuring the time taken for an object to pass a fixed point. A light gate can be used connected to a computer interface. Instantaneous speed = length of mask / time
What is acceleration?
Acceleration is the change in speed per second.
How can acceleration be found?
A = (v-u) / t
What is a speed-time graph?
A time graph is used to show how the speed of an object changes with time.
What can forces change?
Speed, shape and direction.
What is a Newton balance?
A Newton Balance is used to measure force. It consists of a spring which will stretch evenly when a force is applied.
When will an object be at rest/constant speed?
When the forces are balanced.
What is weight?
The force acting on an object due to gravity.
How is weight defined?
W = mg
What unit is mass?
Kg
What unit is weight?
N
What is gravitational field strength?
The force per unit mass measured in Nkg -1.
What is newtons 2nd law?
An object will accelerate at a constant rate when acted on by a constant unbalanced force.
What is force (unbalanced)?
Fun = ma
What are seatbelts used for?
To provide an unbalanced force in the opposite direction of travel should a car crash.
