Physics

Question 1

Explain why sound travels fastest in solids.

Question 2

Describe how to convert a s-t graph to a v-t graph

Answer 2

y coordinate of a v-t graph = gradient of a s-t graph (e.g. increasing grad of s-t, vel. increases)

Question 3

(For reflection) When mirror rotates x degrees, the normal rotates ? degrees

Question 4

(For reflection) When mirror rotates x degrees, (angle of incidence + angle of reflection) increases by ? degrees

Question 5

When air pressure

Question 6

List out all base quantities, their SI unit and symbols (6 of them, exclude luminous intensity)

Question 7

Define derived quantities

Question 8

List out all factors n their respective prefix and symbol (4 multiples, 5 sub-multiples)

Question 9

State size of an atom n size of the earth

Question 10

State the 4 measuring instruments, the length they can measure and their precision in cm

Question 11

How to minimise errors while using a metre rule (4 ways)

Answer 11

1. Avoid zero errors.
   - Take care to line up the end of the object with the zero of the scale.
2. Avoid parallax errors.
   - Position your eye vertically above the scale such that your line of sight is perpendicular to the rule
   marking.
   3.Taking several readings and calculating the average
   4.due to wear and tear on the ends of a ruler, it will be better to measure from another point and subtract it from the final reading instead of beginning at 0.0 cm.

Question 12

State what a pendulum is affected by n how so, and what it isnt affected by

Answer 12

-The period of a pendulum is affected by its length. The larger the length, the longer the period.
-The period of a pendulum is not affected by the mass of the pendulum bob.

Question 13

Define scalar and vector quantities and their examples

Question 14

Deleceration happens when v and a are in ?

Question 15

Define distance and displacement

Answer 15

Distance= Total length covered by a moving object regardless of the direction of motion.

Displacement=Distance measured in a straight line in a specified direction.

Question 16

Define instantaneous speed/vel.

Answer 16

Speed (or velocity) at a particular instant.

Question 17

how to calculate speed of a ticker tape

Answer 17

the time taken for each interval (derived by e.g. 1s/50 if f=50 dots per second) x no. of intervals= total time.

-then use std triangle to find speed of ticker tape

Question 18

Acceleration occurs when..

Answer 18

-a change in speed
-a change in direction
-or both

Question 19

Conditions for action-reaction pair

Answer 19

• [1] The two forces must be of the same nature (eg. gravitational, frictional).
• [2] The two forces must happen at the same time (ie. one force is not the cause of the other).
• [3] The two forces must act on different bodies.
• [4] The two forces must be equal in magnitude but in opposite direction to each other.

Question 20

recall the shape of a v-t graph for free fall

Question 21

state principle of moments

Answer 21

When a body is in equilibrium, the sum of clockwise moments about a point is equal to the sum of anticlockwise moments about the same point.

Question 22

Conditions for equilibrium

Answer 22

-no Fr
-no resultant moment

Question 23

How to find CG for irregular objects + precautions + conclusion

Answer 23

1. Make three holes near the edge of the lamina. The
   holes should be as far apart as possible from one
   another.
2. Suspend the lamina freely from a pin.
3. Hang a plumb line from the pin in front of the lamina.
4. When the plumb line is steady, trace the line on the
   lamina.
5. Repeat steps 2 to 4 for the other two holes.

Precautions:
1. The holes must be small so that not too much of the
lamina is removed.
2. The lamina should be free to swing about its point of
suspension.
Conclusion:
The point of intersection of the three lines is the position of
the centre of gravity of the lamina.

Question 24

How to make an object more stable

Answer 24

-lower cg
-increase base area

Question 25

Describe cg for stable, unstable n neutral equilibrium

Answer 25

stable eq. = cg rises when tilted, vertical line thru its cg falls within base area + restoring moment

unstable eq. = cg lowers when it is tilted, vertical line thru its cg falls outside its base area + overturning moment

neutral eq. = remains at the same height when displaced, vertical line thru its cg coincides with the normal reaction force

Question 26

State KE n GPE formula

Answer 26

Ek = 1⁄2mv2 n EP = mgh

Question 27

State principle of conservation of energy

Answer 27

• Energy cannot be created or destroyed.
• It can only be transferred from one store to another.
• The total energy in an isolated system is constant.

Question 28

Formula for efficiency and power

Answer 28

P(in W or J/s) =W/t or E/t + Efficiency = Useful Energy Output/ Total Energy Input x 100%

Question 29

state 1 +ve n -ve about solar power/hydropower/wind power

Answer 29

No harmful gases are produced when
producing electricity. + High production costs (but for wind power noise pollution)

Question 30

formula of pressure at a point due to a column of fluid

Answer 30

hpg (p stands for density)

Question 31

Define wavefront

Answer 31

An imaginary line joining all points on a wave that are in phase.

Question 32

Define longitudinal and transverse waves

Answer 32

Longitudinal waves:
Waves that travel in a direction parallel to the direction of vibration of particles.

then transverse just perpendicular

Question 33

Define compression and rarefraction

Answer 33

Compression: Regions in the longitudinal wave where air pressure
is slightly higher than the surrounding air pressure.

then rarefraction is just lower

Question 34

deep to shallow water, wavelength (?) , freq. ? and thus speed ?

Answer 34

wavelength decreases, f is the same (determined by dipper) thus speed is slower in shallow water

Question 35

state how to draw displacement-dist and displ-time wave graph

Question 36

state how to draw the deep to shallow water refraction diagram

Question 37

list out all types of EM waves and their wavelength and freq.

Answer 37

Ronald Macdonald Is Very Ugly X-cept Gavin (Radiowave has longest wavelength and hence lowest freq)

Question 38

Visible light spectrum

Answer 38

ROY Gave Birth In Vietnam (Red has longest wavelength, hence lowest freq.)

Question 39

State real-life application of all the types of EM waves

Answer 39

i. radiowaves (e.g. radio and television communication, astronomy and RFID tags)
ii. microwaves (e.g. mobile (cell) phones, microwave oven and satellite television)
iii. infra-red (e.g. infra-red remote controllers, intruder alarms and thermal imaging)
iv. light (e.g. optical fibres for medical uses and telecommunications)
v. ultra-violet (e.g. sunbeds, bank note authentication and disinfecting water)
vi. X-rays (e.g. medical radiology, security screening and industrial defect detection)
vii. gamma rays (e.g. sterilising food, detection of cancer and its treatment)

Question 40

State 2 properties of EM waves

Answer 40

They travel at the same speed (3.0 × 10*8 m s–1) in vacuum.
Electromagnetic waves are transverse waves.
They all obey the wave equation, v = ƒλ.

Question 41

State the 3 steps for drawing reflection ray diagram

Question 42

State the 6 situations for lenses (u n v thing) and their applications

Question 43

State the 5 formulas of refraction (n for some, their special conditions)

Question 44

State 2 advantages of optical fibres

Answer 44

3. They are also lighter than copper wires.
4. They are becoming cheaper to manufacture than copper wires.

Question 46

For potential divider qns, think about ? first

Answer 46

voltage first

Question 47

If confused for current qns, ?

Answer 47

do your own simple calculations with simple numbers