physics sem 1

Question 1

describe the work of Aristotle

Answer 1

Aristotle (384-322 BC) was an ancient Greek philosopher. He discovered many of the simple mechanics in physics such as all motion requires a force and heavier objects fall faster than natural ones. Much of his work was based on observations of the world around him including natural motion in which objects moves to their natural spaces like air rising.

Question 2

describe the world of Newton

Answer 2

Newton 91642-1727) can be considered the father of classical mechanics. It uses a lot more mathematics, focusing mainly on motion ie Newton’s 3 Laws as well as work and energy. Newton himself is said to have discovered gravity or his famous prism experiment depicting that white light was made up of the colours of the rainbow and invented other things like calculus.

Question 3

distance

Answer 3

Distance = total ground covered by the object on the journey. It is scalar

Question 4

displacement

Answer 4

Displacement = the change in position of the object from the start to the end of the journey. It is vector.

Question 5

speed

Answer 5

Speed = a measure of how far an object moves in a given time. It is scalar.

Question 6

velocity

Answer 6

Velocity = the speed and direction in which an object is travelling. It is vector

Question 7

acceleration

Answer 7

Acceleration = a measure of the rate of change of velocity. It is vector

Question 8

force

Answer 8

Force = Force is a push or pull which tends to change the state of rest or of uniform motion , the direction of motion, or the shape and size of a body. When 1 N of force acts on 1kg object it will accelerate at 1 ms-2. It is vector

Question 9

inertia

Answer 9

Inertia = The property of matter that causes it to resist any change in its state of rest or of uniform motion.

Question 10

scalar

Answer 10

Scalar = quantities that are measured with a number and units eg length (cm), temperature (deg C), times (s)

Question 11

vector

Answer 11

Vector = quantities that are measured with a number and untis but also have a specific direction eg velocity (m/s north), weight (N down), friction (N backwards)

Question 12

gravity

Answer 12

Gravity is a non contact force where two objects are attracted to each other by their masses which are creating a gravitational field. An object with a larger mass with form a larger gravitational field and have a stronger force of gravity within in this field. The further an object is from the mass that’s attracting it the weaker the gravitational attraction will be. Gravitational fields acceleration objects towards each other ie on earth we experience this as acceleration towards the centre of earth.

Question 13

gravitational field strength

Answer 13

Gravitational field strength is an acceleration due to gravity aka freefall. This is a vertical acceleration of 9.80ms-2 downwards.

Question 14

mass

Answer 14

Mass = the amount of matter in an object (kg)

Question 15

weight + calculation

Answer 15

Weight =a force which is caused by the pull of gravity acting on a mass (N)
W = mg

Question 16

speed calculation

Answer 16

speed = d/t

Question 17

velocity calculation

Answer 17

v = s/t

Question 18

acceleration calculation

Answer 18

a = (vf-vi)/(tf-ti)

Question 19

distance time graphs

Answer 19

• The gradient gives the speed of the object
  
  • Use larger values when calculating gradient to make measurement error smaller

Question 20

displacement time graphs

Answer 20

• The displacement of an object from its defined starting position
  
  • The gradient (rise/run) gives the velocity of the objects
  • A negative gradient means you have a negative velocity and you are going back towards the starting point of your journey.

Question 21

s-t horizontal line

Answer 21

0 gradient, 0 velocity, object is stationary

Question 22

s-t line going up

Answer 22

positive gradient, constant velocity in direction of positive displacement

Question 23

s-t line going down

Answer 23

negative gradient, constant velocity in direction of negative displacement (going back to starting position)

Question 24

s-t start flat then go up

Answer 24

increasing gradient, increasing velocity, accelerating

Question 25

s-t start going up then flat

Answer 25

less positive gradient, decreasing (less positive) velocity, decelerating

Question 26

s-t start flat then go down

Answer 26

more negative gradient, more negative velocity, negative acceleration (speeding up but going in opposite direction)

Question 27

s-t do down then flat

Answer 27

less negative gradient, less negative acceleration (positive acceleration in negative direction of travel)

Question 28

speed time graphs

Answer 28

- The gradient is acceleration - The steeper the positive gradient the faster the accelerations - A negative gradient is decelerating - Horizontal line is constant speed

Question 29

velocity time graphs

Answer 29

- The gradient is the accelerations - A horizontal line if a constant velocity with no acceleration - If velocity is 0 the object is stationary Negative velocity means moving backwards in the opposite directions

Question 30

change in velocity

Answer 30

Velocity changes when there is a change in magnitude (speed) or/and a change in direction. Acceleration includes speeding up, slowing down (deceleration) and changing direction (centripetal acceleration)

Question 31

v-t horizontal line

Answer 31

0 gradient, 0 acceleration, constant velocity

Question 32

v-t line going up

Answer 32

positive gradient, constant acceleration in direction of positive displacement

Question 33

v-t line going down

Answer 33

negative gradient, constant acceleration in direction of negative displacement.

Question 34

v-t start flat then go up

Answer 34

acceleration is increasing

Question 35

v-t go up then start to flatten

Answer 35

decreasing acceleration but velocity is still postive

Question 36

v - t start flat then go down

Answer 36

gradient becoming more negative, more negative acceleration - decelerating

Question 37

v-t go down then start to flatten

Answer 37

less negative gradient, less negative acceleration - decelerating slower

Question 38

displacement on v-t graphs

Answer 38

the area under the line on a velocity time graphs gives the displacement. You must calculate using triangles (A= 1/2 x b x h) and rectangles (A = b x h). if v is negative then it is the area above the line. for distance you add everything regardless of sing, for displacement be careful of the sign (know if v is negative then s is negative for that shape)

Question 39

how do you draw graphs to solve acceleration problems

Answer 39

You would draw a velocity time draw and then calculate the gradient of the line in order to find the acceleration which you can then plot on a separate graph with time - in these the area under the curve is velocity.

Question 40

what are the equations of motion for constant acceleration

Answer 40

vf = vi + at vf^2 = vi^2 + 2as s = vi x t + 1/2 at^2 not given : s = 1/2 (vi+vf) t

Question 41

what is special about problems with falling objects?

Answer 41

In the case of falling objects your acceleration is automatically 9.80m/s/s. This is because falling objects are accelerating downwards due to gravitational filed strength