Horizontal force pulls a body of 2.25 kg a distance of 8 m across a rough horizontal surface, coefficient of friction 1/3. The body moves with constant velocity and the only resisting force is due to friction. Find the work done against friction. [2 marks] Q2
The point A is 4 m vertically above the point B. A body of mass 0.2 kg is projected from A vertically downwards with speed 3 m/s. Find the speed of the body when it reaches B. [7 marks]
Q3
A body of mass 2 kg, passing through two points A and B. The speeds of the body as it passes A and B are 1 m/s and 4 m/s respectively. The resistance against which the body falls is 9.6 N. Use energy considerations to determine the distance AB. [5 marks]
Q4
A particle is projected horizontally with a velocity of 39.2 ms-2. Find the horizontal and vertical components of the velocity of the particle 3 seconds after projection. Find also the speed and direction of motion of the particle at this time. [6marks]​

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =