Mechanics and Heat Flashcards
What is instantaneous speed?
Instantaneous speed is the average speed over a very short time interval
What is the experiment used to find the instantaneous speed?
A light gate connected to an electronic timer is set up on a ramp. A trolley with a mask, measured using a ruler, on it is let go from the top of the ramp. When the mask first intercepts the light gate the electronic timer starts when the mask is no longer intercepting it the electronic timer stops.
We then use the equation:
Length of mask(d)
Time through light gate (t)
What is the experiment used to measure instantaneous speed involving one trolley and one light gate?
A ramp is set up with one light gate positioned on it. A trolley with a mask on it is let go from the top of the ramp. When the mask on the trolley first breaks the beam of the light gate the electronic timer connected to it starts and when the mask stops breaking the beam the electronic timer stops. The distance of the mask is measure using a ruler so we can then use the equation:
Speed= length of mask
Time through light gate
What is a vector quantity?
A quantity that can be completely described by stating its magnitude and direction
What is a scalar quantity?
A quantity that can be completely described by stating its magnitude
TRUE OR FALSE
Distance is a vector
FALSE
Distance is a scalar quantity
Name a vector quantity?
Displacement
What is the difference between distance and displacement?
Displacement is the length measured from the starting point in a straight line and both its magnitude and direction must be stated. Whereas distance is the total length travelled no matter what direction as it is only described by its magnitude.
Which is a scalar quantity?
Velocity or speed
Speed is a scalar quantity
TRUE OR FALSE
Velocity is a vector quantity
TRUE
What is meant by acceleration?
Acceleration is the change in velocity per unit time
What is the equation for acceleration?
Acceleration= final velocity-initial velocity
Time
What is the sentence that must be written when answering a question involving a speed-time graph?
Distance=area under speed time graph
What does a flat velocity time graph dictate about the velocity?
It is constant
What does a straight upwards line in a velocity time graph tell you about the velocity?
A constant acceleration
What does a straight downwards line on a velocity time graph tell you about the acceleration?
There is a constant deceleration
When an object’d speed or direction changes what is it said to be?
Accelerating
What determines the motion of an object?
The forces acting upon them
What is a force?
The push or pull on an object
What three things can forces change of an object
Speed
Direction
Shape
What does a newton balance measure?
Force
What is meant by the weight of an object?
Weight is the measure of the force due to gravity acting on the object
What is weight measured in?
Newtons (N)
What is meant by mass?
Mass is the quantity of matter in an object
What is mass measured in?
Kilograms (kg)
What is meant by gravitational field strength?
Gravitational field strength is the weight per unit mass
What is gravitational field strength measured in?
Newtons per kilogram (N/kg)
What is the equation involving weight, mass and gravitational field strength?
Weight= mass x gravitational field strength
What the gravitational field strength on Earth?
10N/kg
TRUE OR FALSE
The greater the mass, the lower the gravity
FALSE
The greater the mass, the greater the gravity
TRUE OR FALSE
The shorter the difference between two masses, the lower the force of gravity between them
TRUE
What is responsible for keeping satellites in orbit?
Gravitational field strength
As the distance from Earth increases what is the consequences on weight?
The weight decreases
TRUE OR FALSE
The further away from Earth you go the less your mass becomes
FALSE
Your mass remains the same everywhere
What does friction do?
Friction opposes an object, in always the opposite direction of the object
What heat loss is there due to friction?
The loss of heat energy and sound energy
Name 2 advantages of friction
Prevents the soles of your shoes slipping
Allows bike breaks to stop bikes
Sand paper on wood
Makes a pencil work
Name 2 disadvantages to friction
Machine parts rub together and wear away
Machines run slower
Name ways in which friction can be prevented
Oiling or greasing the surface
Using wooden rollers
A layer of wax
A layer of air
What ways can you increase friction
Choosing surfaces that cause high friction
Increasing surface area
Increasing air resistance
What two factors effect aerodynamic drag?
The shape and size of the object
The speed of the moving object
What happens to the aerodynamic drag when the speed increases?
The aerodynamic drag also increases
What is streamlining?
The shape of an object which reduces the degree of drag or resistance to motion through a liquid or a gas
In what ways do cyclists reduce friction?
Stream lines helmet
Thin tyres
Crouched cycling position
In what ways do parachuters increase friction
The shape of their parachute
The light wieght
The large surface area
TRUE OR FALSE
Force is a scalar quantity
FALSE
Force is a vector quantity as it is completely described by both magnitude and direction
What are balanced forces?
Forces which are acting in the same direction but are equivalent
What are equivalent forces equal to
No force at all
What is Newton’s first law?
An object will remain at rest or continue at a constant speed in the same direction unless acted upon by an unbalanced force
What effect does increasing the mass have on friction and acceleration?
If the mass where to increase the force of friction would also increase and therefore it will decelerate.
What is a Newton?
A Newton is the unit of force required to accelerate a mass of 1kg 1m/s
What is meant by the resultant force?
The resultant force is the vector sum of the individual (component) forces acting on an object
When do you get a resultant force?
When two or more forces act thy can be replaced by one force which has the same effect, this is the resultant force
What is Newtons 2nd law?
If the forces acting on an object are unbalanced then the object will accelerate
TRUE OR FALSE
The acceleration is directly proportional to the force
TRUE
What is inversely proportional to acceleration?
Mass
What is the equation involving force, mass and acceleration?
Force= mass x acceleration
What is the acceleration due to gravity equal to??
Gravitational field strength
If a projectile is released from very high at the right speed what won’t it do?
Hit the ground because it will go into orbit
What two independent motions are involved in a projectile?
Constant speed and constant acceleration
In which direction is constant speed?
Horizontal
Which direction is constant acceleration?
Vertical
Why does an object follow a curved path?
Because due to its motion being a combination of a constant horizontal speed and a constant vertical acceleration
What is Newton’s third law?
If A exerts on B, B exerts an equal but opposite force on A
Explain this Newton pair: a golf club striking a golf ball
The golf club exerts a force (action) forwards in the ball and the ball exerts an equal force (reaction) backwards on the club
What is the equation involving momentum, mass and velocity
Momentum= mass x velocity
TRUE OR FALSE
Momentum is a scalar quantity
FALSE
Momentum is completely described by stating its magnitude and direction
What is the law of conservation of linear momentum?
In the absence of net external forces, the total momentum before is equal to the total momentum after
What is the equation for a collision when the objects don’t stick together?
MaUa+MbUb=MaVa+MbVb
What is the equation o a collision when the objects do stick together?
MaUa+MbUb=(Ma+Mb)V
What is meant by work done?
Work done is the measure of energy transfer
What us temperature
Temperature is the measure of how hot a substance is
What is heat
A form of energy
TRUE OR FALSE
Heat travels from a hot object to a cd object
TRUE
TRUE OR FALSE
The greater he difference of hot and cold the more heat will be transferred
TRUE
What is specific heat capacity?
Is the quantity of energy required to change the temperature of 1kg of a substance by 1°C
What is latent heat?
The heat energy required to change a substances’ state.
Is there a change in temperature when a substance changes state?
No
What is specific latent heat?
The number of joules of energy required to change the state of 1kg of a substance without a change in temperature
