Other Physics Answers

The absorption of electromagnetic radiation by chlorophyll a and chlorophyll b present in green plants peaks at wavelengths 𝜆𝑎 = 6.80 × 10−7𝑚 and 𝜆𝑏 = 6.44 × 10−7𝑚 respectively. Determine the energy of the photons at each wavelengths:

a) 𝜆𝑎

b) 𝜆𝑏

Photosynthesis of glucose (C6H12O6) can be summarized in the following net reaction:

6𝐶𝑂2 + 6𝐻2𝑂 → 𝐶6𝐻12𝑂6 + 6𝑂2

The total energy needed to make one CO2 molecule to react is 2.34 × 10-18 J = 14.6 eV. On, average how many photons must be absorbed by a CO2 molecule;

c) In chlorophyll a to react

d) In chlorophyll b to react.

A pumpkin leaf is exposed to a wind flowing at 2.5 ms-1 when the air temperature is 20°C. The width of the leaf is 15 cm and it is at a temperature of 28°C.

a) Determine the Reynold’s and Garashof number.

b) Compute the rate of convective heat transfer.

The net radiation measured over a dense forest in Naitasiri at noon on a cloudless June day was 730 Wm-2. Given the following other measurements made over the forest, calculate the temperature of the top of the forest canopy, assuming that the foliage radiated like a perfect black body.

Downward solar radiation 900 Wm-2 Albedo 0.10 (10%)

Downward longwave radiation 400 Wm-2

(HINT: Stefan’s Law B = σT4 where σ is 56.7 × 10-9 Wm-2K-4, and T is the temperature in degrees Kelvin.)

Puffin birds which are similar to penguins have a height of around 30 cm and radius of 8 cm when standing on land. Treating a puffin as a vertical cylinder, calculate the mean direct radiation flux Sb incident per unit body area, when the solar elevation angle is 15° and the direct irradiance at normal incidence Sp is 745 Wm-2. [3 marks]

a) A caterpillar of radius 0.5 cm and length 3.5 cm is suspended in air. If the caterpillar is maintained at, Ts = 40 °C and the air temperature remains constant at T = 25°C, calculate:

a) The resistance to radiative heat transfer [1 mark] b) The power radiated by the sphere

Consider a location in Lautoka, Fiji which has a latitude of 18.28 ̊S and calculate the following parameters.

a) Solar zenith angle at local solar noon for 30th May, 2021

b) Daylength for 30th May, 2021

c) Solar attitude at solar noon and 3 pm on 30th May, 2021

Assuming a cloudless sky with the air temperature of 25°C, estimate:

a) The downward longwave irradiance at the ground.

b) The atmospheric emissivity.

c) The upward longwave irradiance.

d) If the same condition exists on a cloudy day with cloud base temperature of 17°C, compute the downward longwave irradiance at the ground.

Hi Sir !

NB : Can you please help me with this problem ?

PROBLEM :

• After leaving the village. the truck maintains a speed of 54 km/h. but 20 m behind it a passenger car starts to accelerate from this speed (a = 2 m.s) and overtakes,completingthe maneuver 20 m in front of it: the length of the truck is 155 m and the length of the car is 45 m. Detemine how long the free distance the driver of the car needs to overtake safely in these circumstances (round up to tens of meterS upward

Thank you in advance !!

A ball is projected from ground level at an initial angle of 33.1 degrees above the horizontal. After

0.74 seconds, the ball hits a wall that is 28.4 meters away. At what height above the ground does

the ball hit the wall?

Two spring with the same force constant of 75 N/m are connected end to end, and the

combination is pulled out by a force of 20 N. a) What is the PE of the stretched springs?

b) If the two springs are connected side-by-side and pulled by the same force, what will be it’s

PE now?

A transverse wave on a rope is given by

Y(x,t) = (0.750m)sin2π [(

t

2.50

s) − (

x

0.400

m)]

a) Find the amplitude, period, frequency, wavelength and speed of propagation.

b) Is the wave traveling in the +x or – x direction?