Forces Flashcards
Is magnetic force a contact or non-contact force?
non-contact force
If the speed at which an object moves through a fluid increases, will the size of the frictional force that acts on it increase, decrease or stay the same?
increase
Is tension a contact or non-contact force?
contact force
Give the general name for the type of quantity that has magnitude and acts in a particular direction.
vector quantity
Is force a vector or a scalar quantity?
vector quantity
Is friction a contact or non-contact force?
contact force
When two objects interact they exert forces on each other. Will these forces act in the same direction or in opposite directions?
opposite
Does Earth exert a contact or a non-contact force on the moon?
non-contact force
Every force on an object is either…
a contact or a non-contact force
Leanne is riding a bike. The forward force from her pedalling is 18N. There is a backward force of 6N from friction and a backward force of 12N from air resistance. Does the speed of the bike increase, decrease or not change?
not change
Is time a vector or a scalar quantity?
scalar quantity
Give the general name for the type of quantity that has magnitude but no particular direction.
scalar quantity
True or false? Forces always act in pairs.
true
Object 1 has a low centre of mass and Object 2 has a high centre of mass. Which object will be more stable?
object 1
True or false? If the vertical line through an object’s centre of mass falls within its base of support then the object will topple over.
false
What name is given to the point at which the mass of an object may be considered to be concentrated?
centre of mass
True or false? Only objects with a symmetrical shape can have a centre of mass.
false
A single force can be resolved into two component forces that act at _____° angles to each other.
90
What name is given to the overall force acting on an object?
resultant force
An object’s mass and its weight are… what?
directly proportional
Jupiter has a gravitational field of 23.6 N/kg. Would your mass be more, less or the same on Jupiter as it is on Earth?
same
Ahmed wants to measure the weight of an object. What instrument should he use?
calibrated spring-balance
True or false? An object weighs less on the moon than it does on Earth.
true
Name the unit which is used for weight.
newtons
Name the universal force of attraction that exists between masses.
gravity
Jupiter has a gravitational field of 23.6 N/kg. Would you weigh more or less on Jupiter than you do on Earth?
more
True or false? An object has the same mass on Earth as it does on Mars.
true
Jupiter’s gravitational field is stronger than Earth’s. On Jupiter, an object’s__________ will be greater than on Earth. What one word completes the sentence?
weight
What is the SI unit for mass?
kilogram
_______ = mass × gravitational field strength
weight
Weight = _____ × gravitational field strength
mass
Weight = mass x ________________ ______ ________
gravitational field strength
Weight is the downward pull of __________ on mass.
gravity
True or false? Weight is a force.
true
What is the main force that must be overcome in order to push an object along a horizontal surface?
friction
Abed uses a force of 1 newton to slide a salt shaker 1 metre across a table. How many newton metres of work has he done?
1Nm
_____ _____ = force × displacement
work done
Work done = ______ × displacement
force
Work done = force × ______________
displacement
How much work is done if a force of 20N is used to move an object 6 metres?
120J
_____ ______ = force × distance
Work done
What is transferred when work is done?
energy
Sara pushed a box of lab equipment along the ground, displacing it by 1 metre. By doing this, she has done __________ on the box of lab equipment.
work
Sara was pushing around a box of lab equipment. She was doing work on it by applying a force and displacing it. Because this work was done against a frictional force that was also acting on the box, the temperature of the box… what?
increased
When a force causes an object to move a distance, __________ is done.
work
What units are used for work done?
joules
When a force causes an object to move, what happens?
work is done and energy is transferred
A force does work on an object when it causes a __________ of the object.
displacement
10 newton metres is equal to how many joules?
10
Work done = _____ × distance
force
Work done = force × ________
distance
Gareth squashed one of his grandma’s favourite cushions as he sat down. True or false? The cushion was squashed by the action of only one force.
false
____ ______ are required to squash an object, otherwise the object would accelerate rather than change shape.
two forces
Two forces are required to squash an object, otherwise the object would __________ rather than change shape.
accelerate
Two forces are required to squash an object, otherwise the object would accelerate rather than change ________.
shape
Johann squeezes a bagel too hard at the supermarket, and it does not return to its original shape when he removes his hand. The bagel has been __________ deformed. What word completes the sentence to show that the bagel has been permanently changed?
inelastically
Inelastic deformation
when an object does not return to its original shape and size when all forces are removed
what’s it called when an object does not return to its original shape and size when all forces are removed
Inelastic deformation
True or false? Objects that can regain their original shapes have energy in their gravitational potential energy stores when their shape is changed by a force.
false
elastic potential energy = ___ × spring constant × (extension)^2
0.5
elastic potential energy = 0.5 × ______ __________ × (extension)^2
spring constant
elastic potential energy = 0.5 × spring constant × _____________
(extension)^2
_______ _________ ________ = 0.5 × spring constant × (extension)2
elastic potential energy
The extension of the spring can be worked out by measuring its __________ when different forces are applied.
length
To work out extension you need to measure the _________ _______ and the final length and find the difference.
starting length
To work out extension you need to measure the starting length and the _______ _______ and find the difference.
final length
_____ = spring constant × extension
force
Force = _________ ________ × extension
spring constant
Force = spring constant × __________
extension
A slinky is stretched by two forces. When the forces are removed, the slinky returns to its original length. The slinky has been __________ deformed.
elastically
True or false? In a non-linear relationship, a change in one variable will always produce a proportional change in the other variable.
false
When you stretch a spring, there is energy in the spring’s __________ potential energy store.
elastic
describe something elastic
return to its original shape and size after being deformed
True or false? In a linear relationship, a change in one variable will always result in a change of the same size in the other variable.
false
Different masses were hung from the spring in order to apply different __________ to it.
forces
Can an object be compressed if only one force is acting on it?
no
The extension of a spring is directly proportional to the __________ applied to it.
force
Doubling the force on a spring will double the __________
extension
Doubling the force on a spring will _______ the extension
double
Doubling the _______ on a spring will double the extension
force
Doubling the force on a spring will double the extension, so they are _______ ___________.
directly proportional
The extension of a spring will increase if the force applied to it… what?
increase
The higher the _______, the greater the extension.
force
The higher the force, the greater the _________.
extension
The higher the force, the ________ the extension.
greater
True or false? When a spring is compressed, it is transferring elastic potential energy to the surroundings.
false
True or false? Work must be done on an object in order to change its shape.
true
When an object moves in a circle the __________ of the object is continually changing, so it’s velocity must be changing too.
direction
When an object moves in a circle the direction of the object is continually changing, so it’s _________ must be changing too.
velocity
A teacher tells his class that a train is moving at 40 miles per hour. Does this tell them the speed of the train, the velocity of the train, or both?
speed
a car travelling at 13 m/s around a bend is an example of what?
changing velocity
Velocity is different from speed because it has both size and… what?
direction
What type of quantity is velocity?
vector
________ is measured in metres per second (m/s).
velocity
Velocity is measured in _______ __ __________ ____.
metres per second (m/s).
What is a typical speed for a person running?
3 m/s
Is speed a vector or a scalar quantity?
scalar
Why is speed a scalar quantity?
doesn’t have direction
_________ = speed × time
distance
Distance = ______ × time
speed
Distance = speed × _____
time
What type of quantity is displacement?
vector
What is a typical speed for a person cycling?
6 m/s
What is the speed of sound in air at 0°C?
330 m/s
True or false? There is no difference between speed and velocity.
false
Scalars have magnitude but vectors have magnitude and __________.
direction
What is a typical speed for a person walking?
1.5 m/s
Displacement is the ________ ________ between start and finish locations.
shortest distance
______________ is the shortest distance between start and finish locations.
Displacement
What are the SI units for speed?
m/s
On a distance-time graph, the _________ always represents speed.
gradient
On a distance-time graph, the gradient always represents ______.
speed
On a ________ _______ _____, the gradient always represents speed.
distance-time graph
____________ = change in velocity / time
acceleration
Acceleration = ________ __ ______ / time
change in velocity
Acceleration = change in velocity / _____
time
The _________ of a velocity-time graph represents acceleration.
gradient
The gradient of a velocity-time graph represents _____________.
acceleration
The gradient of a ________ _____ _____ represents acceleration.
velocity-time graph
____________ = (final velocity – initial velocity) / time
acceleration
acceleration = (final velocity – initial velocity) / ____
time
acceleration = (______ _______– initial velocity) / time
final velocity
acceleration = (final velocity - _____ ________) / time
initial velocity
a = (v - u) / t
what does the u represent?
initial velocity
a = (v - u) / t
what does the a represent?
acceleration
a = (v - u) / t
what does the v represent?
final velocity
a = (v - u) / t
what does the t represent?
time
What is a negative acceleration called?
deceleration
What effect does a parachute have on the frictional force acting on the parachutist?
increase it
True or false? Acceleration due to gravity (g) is the same for any object at a given point on the Earth’s surface.
true
What name is given to the steady speed of a falling object when the downwards and upwards forces on it are balanced?
terminal velocity
A sky-diver is falling through the Earth’s atmosphere at terminal speed. What is happening to the energy in her kinetic energy stores?
it is staying the same
What is the resultant force on an object that has reached its terminal velocity?
0
True or false? Acceleration due to gravity (g) is unaffected by atmospheric changes.
true
True or false? Acceleration due to gravity (g) will be the same on the top of a mountain as it is down a mineshaft.
false
A sky-diver is falling through the Earth’s atmosphere at terminal speed. What is happening to the energy in her gravitational potential energy stores?
decreasing
An object falling through a fluid originally accelerates due to what force?
gravity
_____ = mass × acceleration
force
Force = _____ × acceleration
mass
Force = mass × ______________
acceleration
True or false? If a book is sitting still on a shelf, the shelf is exerting a constant force on the book.
true
To calculate the acceleration of an object you need to know the resultant force acting on the object. What else do you need to know?
mass of object
The same resultant force acts on objects 1 and 2. Object 1 accelerates at 2m/s² and Object 2 accelerates at 5m/s². Which object has the greater mass?
object 1
If a coach is accelerating at ~2m/s², it is accelerating at __________ 2m/s². What word completes the sentence?
approximately
The “~” symbol means ________________.
approximately
Name the main resistive force that opposes the driving force when a vehicle is moving.
air resistance
When a vehicle travels at a steady speed the driving force and the resistive forces must be __________. What one word completes sentence?
equal
An apple is resting on a table. Claire says that there are no forces acting on the apple because it is not moving. Is she right?
no
________ __ _____________ = mass × change in velocity
change in momentum
change in momentum = ____ × change in velocity
mass
change in momentum = mass × ________ __ _________
change in velocity
_____________ = force / mass
acceleration
Acceleration = ______ / mass
force
Acceleration = force / _____
mass
True or false? A gun recoils backwards as it fires because as the gun exerts a force on the bullet, the bullet also exerts an equal and opposite force on the gun.
true
True or false? Newton’s third law of motion applies in collisions but not in static situations.
false
Whose name completes the gap? According to __________’s third law of motion, every action has an equal and opposite reaction.
Newton
A van is moving at 10m/s. True or false? If the resultant force on this van is zero, the van will slow down and stop.
false
Objects tend to continue in their current state, if at rest or uniform motion. What is the term for this tendency?
inertia
inertia
the tendency for objects to continue in their current state
In addition to acceleration, what do you need to know to calculate inertial mass?
resultant force
Inertial mass is a measure of how difficult it is to change the __________ of an object. What word completes the sentence?
velocity
What happens to the driver’s reaction time (measured in seconds) after he has consumed alcohol?
increases
A wet road will increase the braking distance but not the _________ distance.
thinking
A ____ ______ will increase the braking distance but not the thinking distance.
wet road
A wet road will increase the ________ distance but not the thinking distance.
braking
Adding the thinking distance of a driver and the braking distance of the car together gives the… what?
stopping distance
_________ _________ = thinking distance + braking distance
stopping distance
Stopping distance = _________ ___________ + braking distance
thinking distance
Stopping distance = thinking distance + _________ _________
braking distance
Which of the following road conditions will increase the braking distance the most?
icy roads
Which part of a road vehicle must be tested to ensure that there is sufficient friction to stop the vehicle in an emergency?
tyres
What effect will worn brakes have on braking distance?
increase it
Which of these is a factor that can affect a car driver’s reaction time?
tiredness
What is the range of a typical reaction time for humans?
0.2 s to 0.9 s
True or false? Tiredness can affect a driver’s reaction time.
true
What happens to the temperature of the car’s brakes when a driver brakes to decelerate quickly?
increases
Jack is driving his car on the motorway. Will the stopping distance be less if he travels at 70 mph or at 80 mph?
70 mph
The distance the car travels during the time it takes the driver to react is called the… what?
thinking distance
When the brakes are applied to slow a car down, the temperature of the brakes… what?
increases
True or false? Everyone has the same reaction time.
false
Car 1 is travelling at 30mph and Car 2 is travelling at 40mph. They have the same mass. Which car will need to apply the greater braking force in order to come to a complete stop within 30m?
car 1
The distance that a vehicle travels while the brakes are working to slow it down is known as the __________ distance. What one word completes the sentence?
braking
For a given braking force, will a higher speed increase or decrease the stopping distance?
increase
Name the force between the brakes and the wheels that does work to slow down the vehicle when the brakes are applied.
friction
What is the name of the force that acts between the brakes and the wheel of a car?
friction
What happens to the temperature of the brakes once the brakes have been applied?
it increases
Once the brakes on a car have been applied, energy is transferred out of which of the car’s energy stores?
kinetic
momentum = ____ × velocity
mass
momentum = mass × _______
velocity
____________ = mass × velocity
momentum
In a closed system the total momentum before an explosion is __________ __________ the total momentum after the explosion.
equal to
A cat with a mass of 5kg is running at a velocity of 8m/s. A dog with a mass of 11kg is running at a velocity of 4m/s. Which animal has the greater momentum?
dog
Velocity = momentum / ____
mass
________ = momentum / mass
velocity
Velocity = ____________ / mass
momentum
A car and a bus are driving along a road at the same speed. The bus has twice the mass of the car. Which vehicle has the greater momentum?
bus
What are the standard units for momentum?
kg m/s
A car travels around a roundabout at a steady speed. Will the car’s momentum be constant?
no
Momentum is a property of objects that are… what?
in motion (moving)
True or false? Momentum is the product of an object’s mass and velocity.
true
True or false? The force a seat belt applies to a passenger in a car that is braking heavily is equal to the passenger’s change in momentum.
false
The law of conservation of momentum applies to what type of system?
closed system
True or false? The momentum of an object changes if its direction changes, even if its speed and mass stay the same.
true
Name a safety feature in a car that helps to reduce injuries by absorbing energy as it changes shape in an accident.
seatbelt
True or false? Seatbelts should always be replaced after a crash because the large forces involved may damage them.
true
Vehicle designers always try to build in safety features that will __________ the rate of change of the vehicle’s momentum in the event of a collision.
reduce
