2 Motion and Force Flashcards
In which part of the graph (A, B or C) is the object moving the fastest?
A
- gradient of the line is the steepest
- more distance covered per time
- faster speed
What is the difference between the force upthrust 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 SI unit for force?
newton or N
What type of force is created between two magnets?
magnetic force
This force can be attractive or repulsive
In which graph/s is the object travelling at a constant speed?
a) and e)
gradient is constant throughout
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
What feature of a velocity-time graph gives the 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 from the starting position
The gradient of the line is increasing, therefore velocity is increasing.
Which sketch (red or green) represents a faster velocity?
Green- more steep line
Object is covering more distance per time
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 SI unit for displacement or distance travelled?
metre or m
F= ma
Make acceleration the subject of the equation
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 (A, B or C) 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
Thrust is created when an object throws something out in one direction- such as gases.
What type of force is reduced if an object is streamlined?
air resistance
Rockets can push gas out and downward and the rocket moves upward. What is the name of this upward force on the rocket?
Thrust
What feature of a velocity-time graph gives the acceleration?
gradient of velocity-time graph
What feature of a velocity-time graph gives the distance travelled?
area under a velocity-time graph
In which graph/s is the object decelerating?
d)
gradient is getting less steep
What can forces do to an object?
- change the speed of the object (accelerate or decelerate)
- change the direction of the object
- change the shape of the object
A horizontal line on a velocity-time graph shows?
constant velocity, no acceleration
A horizontal line on a distance-time graph shows what?
That the object is not moving, has zero speed
If a book is a rest on a table, what two forces are acting on it.
downward gravitational pull (or weight)
upward reaction force from table
If an object accelerates at 10 m/s2. How fast would it be travelling after 10 s if it started at rest?
It will gain 10 metres per second every second.
After 10 s if should be travelling at 100 m/s!
What feature of a distance-time graph gives the velocity?
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
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 (A, B or C) is the object stopped?
B
Gradient is zero therfore speed is zero- obejct is not moving
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
In which graph/s is the object travelling at a constant speed?
a) and e)
gradient is constant throughout
How would you sketch a d-t graph of an object accelerating away from a point
The gradient of the line is increasing
speed is increasing
object is accelerating
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
In which graph/s is the object decelerating?
d)
gradient is getting less steep
How do you find the instantaneous speed from a distance time graph?
Calculate the gradient of the line at that instant.
Draw a triangle and calculate
speed = rise/ run - distance travelled/ time
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
Why does the moon have less gravity (or gravitational field strength) than the Earth?
The moon has less mass than the Earth
Sketch a d-t graph of an object stationary at 3 metres.
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
Which ticker tape shows an object which is decelerating then accelerating?
ticker tape E
- dots get closer together, then further apart
- object is covering less distance per unit time, then more distance per unit time.
- object is slowing down then speeding up, decelerating, then accelerating
In which graph/s is the object at rest?
b)
gradient is zero
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
In which part of the graph (A, B or C) is the object stopped?
B
Gradient is zero therfore speed is zero- obejct is not moving
Which ticker tape shows an object which is decelerating then accelerating?
ticker tape E
- dots get closer together, then further apart
- object is covering less distance per unit time, then more distance per unit time.
- object is slowing down then speeding up, decelerating, then accelerating
In which part of the graph (A, B or C) is the object moving the slowest?
C
- gradient of the line is the shallowest
- less distance covered per time
- slower speed
