Book Two

Question 1

*what is distance? + SI unit

Answer 1

the length of the actual path followed by a body
metre

Question 2

*what is displacement? + SI unit

Answer 2

the shortest distance between two points
metre

Question 3

*what is speed? + formula, SI unit

Answer 3

the rate of change of distance
average speed = tot. distance moved / tot. time taken
ms^-1

Question 4

*what is velocity? + formula, SI unit

Answer 4

the rate of change of displacement
average velocity = tot. displacement / tot. time taken
ms^-1

Question 5

*what is acceleration? + formula, SI unit

Answer 5

the rate of change of velocity
average acceleration = change in velocity / time taken
ms^-2

Question 6

*equations of motion

Answer 6

v = u + at
s = ut + 1/2at^2
v^2 = u^2 + 2as

Question 7

*what is acceleration of free fall?

Answer 7

acceleration due to gravity
9.81ms^-2
g

Question 8

*displacement-time graph (s-t graph)

Answer 8

• gradient is uniform velocity
• straight line is stationary/at rest
• inward curve is for acceleration
• outward curve for deceleration

Question 9

*velocity-time graph (v-t graph)

Answer 9

• gradient = acceleration
• straight line is uniform acceleration
• uniform deceleration
• inward curve is non-uniform increasing acceleration
• outward curve is non-uniform decreasing acceleration

Question 10

*what is newtons 1st law?

Answer 10

a body will remain in its uniform state of rest or motion on a straight line unless acted upon by a resultant force

Question 11

*what is inertia?

Answer 11

the reluctance of a body to change its state of rest or motion

Question 12

*what is mass?

Answer 12

the property of a body that resists change in its state of motion

Question 13

*what is momentum? + formula, SI unit

Answer 13

the product of mass and velocity
p = mv
kgms^-1

Question 14

*what is the principle of conservation of momentum?

Answer 14

it states that total momentum of a system remains constant unless an external force acts on it

Question 15

*what is newtons 2nd law?

Answer 15

rate of change of momentum is directly proportional to the resultant force acting upon it

Question 16

*what is a newton?

Answer 16

the force that gives unit mass unit acceleration

Question 17

*what is impulse? + formula, SI unit

Answer 17

the product of force and time
impulse = force x time
Ns or kgms^-1

Question 18

*what is newtons 3rd law?

Answer 18

for every action force there is an equal and opposite reaction force

Question 19

*what is weight? + formula, SI unit

Answer 19

this is force of gravity acting on a body
W = mg
N

Question 20

*nb:

Answer 20

mass doesn’t vary from place to place but weight does since g isn’t constant

Question 21

*what is a projectile?

Answer 21

any object thrown in the earths gravitational field

Question 22

*equations of projectile motion : vertical motion

Answer 22

• max. height
  hmax. = u^2sin2x / 2g
• time taken to reach hmax.
  t = usinx / g
• time of flight = 2t
  2t = 2usinx / g
  alt.
  t’ = 2usinx / g

Question 23

*equations of projectile motion : horizontal motion

Answer 23

• range
  R = u^2 / g (sin2x)
  for a given velocity or projection, R is maximum when sin2x = 1 - x = 45*
  then,
  Rmax = u^2 / g

Question 24

*what are collisions? + types

Answer 24

interaction between bodies
- elastic and inelastic collisions

Question 25

*what are elastic collisions?

Answer 25

where kinetic energy is conserved

Question 26

*what are inelastic collisions?

Answer 26

where kinetic energy is not conserved

Question 27

*before collision = after collision formula

Answer 27

m1u1^2 + m2u2^2 = m1v1^2 + m2v2^2

Question 28

*equations of collisions

Answer 28

• m1(u1 - v1) = m2(u2 - v2)
• m1(u1 - v1)(u1 + v1)=m2(v2 - u2)(v2 + u2)
• u1 - u2 = - (v1 - v2)
• u1 = v1 + v2
• u1 = v2 - v1

Question 29

*what is force? + formula, SI unit

Answer 29

a push or pull on one body by another
F =ma
N

Question 30

*types of forces

Answer 30

weight - gravitational force on a body
upthrust - upward force experienced by a body placed in a fluid that causes it to float
thrust - forward force from an engine
air resistance - frictional force that resists motion of a body in air
tension - force in a stretched material
friction - the resistance of the sliding or rolling of one body over another
contact - force between two bodies

Question 31

*what is upthrust?

Answer 31

upward force experienced by a body immersed in a fluid which causes a pressure on the body exerted by the fluid

Question 32

*what is archimedes principle?

Answer 32

a body immersed in a fluid experiences an upthrust equal to the weight of the displaced fluid.

Question 33

*what is friction? + types

Answer 33

the resistance of the sliding or rolling of one body over another
- static and dynamic friction
- static > dynamic

Question 34

*what is static friction?

Answer 34

friction that occurs when a body is just about to start moving

Question 35

*what is dynamic friction?

Answer 35

friction that occurs between surfaces of bodies in motion

Question 36

*positive effects of friction

Answer 36

• gives feet, shoes, tyres grip on the ground
  -used in most braking systems

Question 37

*negative effects of friction

Answer 37

• causes wear and tear of moving parts of machinery
• generates unwanted heat in machines

Question 38

*how to reduce friction in machines

Answer 38

• using roller bearings/ball bearings
• applying grease/oil

Question 39

what is centre of gravity?

Answer 39

a point on a body where the total mass or weight tends to act

Question 40

what is a moment? + formula, SI unit

Answer 40

the product of force and its perpendicular distance from the pivot
moment = force x perpendicular distance from the pivot
Nm

Question 41

principle of moments

Answer 41

for a body to be in equilibrium, the sum of clockwise moments about a point must equal to the sum of anticlockwise moments about that same point

Question 42

what is a torque? +Formula, SI unit

Answer 42

this is the moment of a force about a point, which causes rotational motion
T = Fd or T = F x r x sinx
Nm

Question 43

conditions for equilibrium

Answer 43

1. resultant moment must equal zero
2. resultant force must be zero

Question 44

*what is density? + formula, SI unit

Answer 44

this is mass per unit volume
density = mass / volume
kgm^-3

Question 45

what is pressure? + formula, SI unit

Answer 45

force acting normally on a surface per unit area
pressure = force / area
Pa

Question 46

what happens to a stationary liquid in an open container?

Answer 46

pressure:
1. acts equally in all directions
2. increases with depth
3. independent of shape of container

Question 47

properties of liquids in hydraulic systems

Answer 47

1. liquids are virtually incompressible
2. if a trapped liquid is put under pressure, the pressure is uniformly transmitted to all parts of the liquid

Question 48

examples of hydraulic machines

Answer 48

1. car brake system
2. arms and diggers of earth movers
3. hydraulic jacks

Question 49

how to measure:
atmospheric pressure
gas pressure
+ commonly used units of pressure

Answer 49

• barometer
• manometer
  bars, atmospheres and mmHg