2 Motion and Force Flashcards
In which part of the graph is the object moving the fastest?
A
-gradient of the line is the steepest
gradient = rise/run = distance/time = speed
What is the difference between upthrust force and reaction force?
Up thrust is created when an object displaces a fluid, such as a boat displacing water.
Reaction force is the upward force on a block which is resting on a solid surface.
What is the unit for force?
newton or N
What feature of a velocity-time graph gives the acceleration?
acceleration = gradient of velocity-time graph
Masses are attracted to each other. Planets are attracted to each other. Name the force acting between them.
Gravitational force
Describe what is happening in the graph and explain how you know.
The object is accelerating or speeding up
Gradient is increasing, therefore velocity is increasing.
If an object has a 50 N force acting North and a 50N force acting south, what is the resultant force?
50 N - 50 N = 0 N
What is the unit for displacement or distance travelled?
metre or m
F= ma
rearrange the equation to give a
a = F/m
Which of the following quantities are vectors?
mass
acceleration
force
speed
velocity
time
acceleration
force
velocity
In which part of the graph is the object travelling back to the start.
C
-gradient of the line is negative
velocity is negative
-travelling in opposite direction to part A
What is the equation for average speed?
average speed = total distance travelled/ time taken
What type of force acts forward on a rocket?
Thrust
the rocket throws gases out backwards to create thrust forward
What type of force is reduced if an object is streamlined?
air resistance
What feature of a velocity-time graph gives the distance travelled?
distance = area under a velocity-time graph
What can forces do to an object?
- change the speed (accelerate or decelerate)
- change the shape
- change the direction
A horizontal line on a velocity-time graph shows?
constant velocity, no acceleration
If a book is at rest on a table, what two forces are acting on it?
downward gravitational pull (or weight)
upward reaction force from table
What feature of a distance-time graph gives the speed?
speed = gradient of distance-time graph
Which ticker tape shows an object which is decelerating?
ticker tape Z
- dots get closer together
- object is covering less distance per unit time
- object is slowing down
Friction forces always oppose motion.
What can be done to reduce friction when an object is sliding on a surface?
- use oil or grease on the surfaces
- make the surfaces smoother
- blow air between the surfaces
In which part of the graph is the object stopped?
B
Gradient is zero therefore speed is zero
What type of force acts upward on the wing of an aeroplane?
Lift
In the equation W=mg, what is g (gravitational field strength or gravity) measured in?
gravity g is measured in N/kg
It is the force which acts on every kg of mass
Describe what is happening to the velocity in this distance time graph.
A –> B velocity is constant
B –> C velocity is zero
C –> D velocity is increasing
D –> E velocity is zero
E–> F velocity is constant but opposite direction
What instrument is used to measure force?
A force meter
acceleration =
The change in velocity per second
a = (v-u)/t
In which graph/s is the object travelling at a constant speed?
a) and e)
gradient is constant throughout
Name three scalar quantites
time
mass
speed
distance
energy
What is the equation which links weight, mass and gravitational field strength?
Weight = mass x gravitational field strenght
W = mg
What is the unit for time?
seconds or s
What force is created in the rope of a swing?
tension
What does this ticker tape show about the movement of the object?
- dots are evenly spaced
- object is covering the same distance per unit time
- object is travelling at a constant speed, it is not accelerating
What is the unit for velocity or speed?
metre per second
m/s
In which graph/s is the object decelerating?
d)
gradient is getting less steep
What type of force is created between two charged particles?
electrostatic force
This can be attractive or repulsive
What is the difference between a vector and scalar quantity?
scalar quantities have magnitude only
vector quantites have both magnitude and direction
If a person has a mass of 100 kg on Earth. What will their weight be?
The gravitational field strength of the Earth is 10 N/kg
W=mg
W = 100 kg x 10 N/kg
W = 1000 N
speed =distance / time
rearrange for distance or d
distance = speed x time
How is mass different from weight?
Mass is the amount of matter an object is made of
(measured in kg or g)
Weight is the gravitational pull on the object which depends on the gravitational field strength of the planet
(measured in Newtons or N)
Why does the moon have less gravity (or gravitational field strength) than the Earth?
The moon has less mass than the Earth
What does this ticker tape show about the movement of the object?
- dots are evenly spaced
- object is covering the same distance per unit time
- object is travelling at a constant speed, it is not accelerating
If you flew to the moon, which would change, your mass in kg or your weight in newtons?
your weight
What is the relationship between force, mass and acceleration?
Force = mass x acceleration
F = ma
This is called Newton’s second law
F= ma
Make mass the subject of the equation
m = F/a
What does this ticker tape show about the movement of the object?
- dots are moving further apart
- object is cover more distance per unit time
- object is speeding up, accelerating
What is the unit for acceleration?
m/s2
What type of force is created between two magnets?
magnetic force
like poles repel
unlike poles attract
speed = distance / time
rearrange to give time t
time = distance / speed
Why are arrows perfect for drawing forces (a vector) quantities?
The arrow size can represent the magnitude of the force. The arrow direction can represent the direction of the force
If a person has a mass of 100 kg on Earth, what will their mass be on the moon?
100 kg
Mass the amount of matter an object is made of
It does not change when on another planet
What is the unit of mass?
kg
kilogram
Stopping distance =
Stopping distance = thinking distance + braking distance
Factors affecting thinking distance are:
- Slower reaction time caused by drugs, alcohol, distractions
- Faster speed
- Poor Visibility such a fog
Factors affecting braking distance are:
- speed
- worn tyres, brakes
- slippery road surfaces
- mass of vehicle
Why does a falling object eventualy reach terminal velocity?
At start of fall, weight force greater than air resistance
An unbalanced force acts causing acceleration
As speed increase, air resistance increases
But weight stays the same
Unbalanced force decrease until weight = air resistance
No unblanced force
No acceleration
Terminal velocity reached
