2.1) What is a scalar quantity?
A scalar quantity is a quantity which only has a magnitude (size) but no specific direction
2.2) What is a vector quantity?
A vector quantity is a quantity which has both a magnitude (size) and a specific direction.
2.4) Give some examples of scalar (8) and vector quantities (6).
Scalar Quantities
• Distance
• Speed
• Mass
• Energy
• Volume
• Density
• Temperature
• Power
Vector Quantities • Displacement • Velocity • Weight • Force • Acceleration • Momentum
2.3) What is the difference between velocity and speed?
Velocity is speed in a stated direction and is a vector quantity while speed is a scalar quantity.
2.5) What is velocity?
Velocity is speed in a stated direction
- 6) What is the equation for:
i) average speed
ii) distance travelled
i) average speed (m/s) = distance (m) ÷ time (s)
ii) Distance (m)= speed (m/s) x time (s)
2.7) What does a distance time graph show?
A distance-time graph shows how the distance of an object moving in a straight line (from its starting position) varies over time.
2.7) How is constant speed represented on a distance-time graph?
Constant speed is represented using a straight line.
2.7) Fill in the sentences:
The slope of the straight line on a distance-time graph represents the __________________ of the speed:
- A very __________ slope means the object is moving at a large speed
- A very __________ slope means the object is moving at a small speed
- A flat, _____________ line means the object is stationary (not moving)
1) magnitude
2) steep
3) shallow
4) horizontal
2.7) How can an object moving at a changing speed be represented on a distance time graph?
It can be represented using a curve.
2.7) On a distance-time graph for an object moving at a changing speed:
• A slope that is increasing means the object is __________________
• A slope that is decreasing means the object is __________________
1) accelerating
2) decelerating
2.7) How can the speed of an object be calculated on a distance-time graph?
It can be calculated from the gradient of the line on the distance-time graph:
Speed= gradient= rise ÷ run
2.8) What is acceleration?
Acceleration is a vector quantity that is defined as the rate of change of velocity.
(In other words, how much an objects velocity changes every second)
2.8) What is the equation to calculate the acceleration of an object?
a = v-u ÷ t
a = acceleration (m/s^2)
v = final velocity (m/s)
u = initial velocity (m/s)
t = time(s)
2.8) An object that speeds up is ________________, and therefore has a positive acceleration
An object that slows down is ________________, and therefore has a negative acceleration.
1) accelerating
2) decelerating
2.9) How do you calculate an object that is moving with uniform (constant) acceleration?
v² — u² = 2ax
x = distance (m) v = final velocity (m/s) u = initial velocity (m/s) a = acceleration (m/s²)
2.10) What does a velocity-time graph show?
A velocity-time graph shows how the velocity of a moving object varies with time.
2.10) How can constant acceleration be represented on a velocity-time graph ?
Constant acceleration can be represented as a straight line
2.10) Fill in the sentences:
The slope of the line on a velocity-time graph represents the ____________ of acceleration:
> A ___________ slope means a large acceleration (or deceleration) i.e the objects speed changes very quickly
> A ___________ slope means a small acceleration (or deceleration) i.e the objects speed changes very gradually
> A flat _____________ line means the acceleration is zero i.e the object is moving with a constant velocity
1) magnitude
2) steep
3) gentle
4) horizontal
2.10) How can the acceleration of an object be calculated using a velocity-time graph?
Acceleration of an object can be calculated from the gradient on the velocity-time graph:
acceleration = gradient = rise ÷ run
2.10) What does the area under a velocity-time graph represent?
The area under a velocity-time graph represents the total distance travelled (or displacement) by an object.
2.11) What is speed?
Speed is the distance travelled by an object every second.
- 11) The simplest way to measure speed of an object is to time how long it takes to travel a known distance and use the average speed equation. To do this, you have to use the right sort of equipment to measure the distance and the time.
i) What type of equipment would you use to measure the distance?
ii) What type of equipment would you use to measure the time?
i) Trundle wheel - for long distances
Metre ruler
Measuring tape
ii) A stopwatch
Light gates
2.11) What are light gates and how can light gates be used to measure time?
Light gates are pieces of digital equipment that allow times to be measured more accurately.
• A flag on the top of the moving object blocks a beam of light as it passes through the light gate, triggering a timer to start
• A second light gate (at some fixed distance away) can be used to stop the timer as the object passes through it.
2.11) How can a single light gate be used to measure the speed of an object?
- The timer measures how long the light gate is blocked for
- The distance travelled is given by the length of the flag passing through the light gate
- The two measurements for distance travelled and time taken can then be used in the speed equation to calculate speed.
2.12) Give the typical speeds of the following:
> walking
> running
> cycling
> car
> passenger aeroplane
> sound
> windWalking = 1.5 m/s Running = 3 m/s Cycling = 6 m/s Car = 10 - 30 m/s Passenger Aeroplane = 200 - 250 m/s Sound = 330 - 340 m/s Wind = 3 - 20 m/s
2.13) Fill in the missing words:
In the absence of _____ resistance, all objects fall with the _________ acceleration - this is called ________________ due to __________ (g).
This value is 10 m/s² - this means that for every second an object falls, its _____________ will increase by 10m/s².
WORD BANK:
gravity velocity air acceleration same
In the absence of __air___ resistance, all objects fall with the __same_______ acceleration - this is called _acceleration_____ due to ___gravity_______.
This value is 10 m/s² - this means that for every second an object falls, its ___velocity__________ will increase by 10m/s².
2.13) Give the typical accelerations of the following:
> Family car
> Falling object
> Rocket
> Formula1car
> Fighter jet> Family car = 2-3 m/s²
> Falling object = 10 m/s²
> Rocket = 30 m/s²
> Formula1car = 50 m/s²
> Fighter jet = 90-120 m/s²2.20) TRUE OR FALSE:
An object moving in a circular orbit at a constant speed has a changing velocity.
TRUE
2.20) Explain why an object travelling in a circular path doesn’t have a constant velocity.
An object travelling in a circular path has a changing velocity even though its speed is constant because the direction of travel is always changing as the object moves along the circular path. As velocity is a vector quantity, so both magnitude and direction are important - even though the magnitude which is speed doesn’t change, its direction changes so the velocity itself changes.
2.21) Finish the sentence:
For an object to travel in a circular orbit there must be …….
a resultant force that acts towards the centre of the circle - this resultant force is known as the centripetal force.
2.21) What is centripetal force?
The resultant perpendicular force towards the centre of the circle required to keep a body in uniform circular motion.
- 21) Identify the centripetal force in these 3 situations:
i) car travelling around a roundabout
ii) ball attached to a rope moving in a circle
iii) Earth orbiting the Sun
i) friction between car tyres and the road
ii) tension in the rope
iii) Gravitational force
2.22) What is inertia?
The tendency of an object to continue in its state of rest, or in uniform motion unless acted upon by an external force. (in other words, an objects resistance to a change in motion)
2.22) What is inertial mass and how can you calculate an object’s inertial mass?
Inertial mass is a measure of how difficult it is to change the velocity of an object. It can be calculated using the equation:
m = F ÷ a m = inertial mass (kg) F = force (N) a = acceleration (m/s²)
2.22) Complete the sentences:
L___________ inertial masses will experience s_______ accelerations
S___________ inertial masses will experience l________ accelerations
1) Larger
2) smaller
3) Smaller
4) larger
This is because inertial mass is inversely proportional to acceleration.
2.24) What is momentum and how do you calculate it?
Momentum is defined as the tendency of an object to keep moving in the same direction. It can be calculated using the equation:
p= m x v
p = momentum (kg m/s) m = mass (kg) v = velocity (m/s)
2.24) TRUE OR FALSE? :
An object at rest has momentum.
FALSE: An object at rest has no momentum - momentum only applies to moving objects.
2.24)TRUE OR FALSE?:
Is it easy to change the direction of an object that has a large momentum.
FALSE: it is harder to change the direction of objects with larger momentums.
2.24) TRUE OR FALSE?:
Momentum can either be positive or negative.
TRUE: As momentum is a vector quantity it can have a positive as well as a negative value.
2.24) The momentum of an object can change if: ….
- the object accelerates or decelerates
- the object changes direction
- the object’s mass changes
2.25) Examples of momentum in an event are collisions. Objects will either:
•collide and move in o___________ directions - this is an e______ collision
•collide and move in the s______ direction together - this is an i__________ collision
1) opposite
2) elastic
3) same
4) inelastic
2.25) Finish the sentence.
When the objects move in opposite directions…..
…. each object will have a different velocity depending on its mass and initial momentum of the system.
2.25) Finish the sentence.
When the objects ove in the same direction together….
…..they will have a combined mass and velocity.
2.23) What does the principle of the momentum state?
The principle of momentum states that in a closed system, the total momentum before an event is equal to the total momentum after the event.
(In other words, momentum is conserved)
2.23)
