Consider a velocity-time graph for a uniformly accelerated body starting from rest is represented as follows.

u: velocity at time t₁

v: velocity at time t₂

If acceleration is represented as a ,then, acceleration is defined as the rate of change in velocity.

This is first equation of linear motion.

When a fireman holds a hose, which is ejecting large amounts of water at a high velocity, then a reaction force is exerted on him by the ejecting water in the backward direction. This is because of Newton’s third law of motion. As a result of the backward force, the stability of the fireman
decreases. Hence, it is difficult for him to remain stable while holding the hose.

Consider an object is moving with a uniform acceleration “a” along a straight line. The initial and final velocities of the object at time t = 0 and t = t are u and v respectively. During time t, let s be the total distance travelled by the object. In uniformly acceleration motion the velocity – time graph of an object is a straight line, inclined to the time axis.

OD = u, OC = v and OE = DA = t.

Let, the Initial velocity of the object = u

Let, the object is moving with uniform acceleration, a

Let, the object reaches at point B after time t, and its final velocity becomes, v.

Draw a line parallel to x-axis DA from point, D from where object starts moving.

Draw another line BA from point B parallel to Y-axis which meets at E at y-axis.

Second Equation of Motion: Distance covered by the object in the given time “t” is given by the area of the trapezium ABDOE.

Let in the given time (t), the distance covered by the moving object = s

The area of trapezium, ABDOE.

Distance (s) = Area of ΔABD + Area of ADOE.

s = ½ x AB x AD + (OD x OE)

s = ½ x DC x AD + (u x t) [∵ AB = DC]

s = ½ x at x t + ut [∵ DC = at]

s = ½ x at x t + ut

s = ut + ½ at².

It is the expression gives the distance covered by the object moving with uniform acceleration.

A n s w e r:
Solubility is the number of grams of the solute that will dissolve in 100 g of the solvent. So as temperature increases due to that the kinetic energy and solubility of salt molecules increases.

Properties of Suspension

• Suspensions are a heterogeneous mixture of two or more substances.
• Particles of the solute do not dissolve in the solvent rather they remain suspended in bulk throughout.
• The size of particles of suspension is large enough to be visible from naked eyes. They are greater than 1 nanometer (?10?^(-9) meter).
• It shows Tyndall effect because of their large size of particles.
• When it is left for some time, particles get settled in the bottom. Therefore, it is not stable.
• The particles in it can be separated through the process of filtration.

Functions of the stomata

1. They allow the exchange of gases (CO2 and O2) with the atmosphere.
2. Evaporation of water from the leaf surface occurs through the stomata. Thus, the stomata help in the process of transpiration.
3. Based on the climatic conditions, it closes or opens its pores to maintain the moisture balance.
4. Allows the intake of carbon dioxide and to give out oxygen during the process of photosynthesis.
5. Stomata remains open during the day and closed at night. This closure at night prevents water from escaping through open pores.

• The stacks of flattened membranous vesicles are called Golgi apparatus.
• It basically stores, packs and modifies the products in vesicles.
• It temporarily stores protein that moves out of the cell through the vesicles of the Golgi apparatus.
• It packs and transports the materials synthesised in Endoplasmic Reticulum to different targets inside and outside the cell.

lasma membrane called a selectively permeable membrane because it regulates the movement of substances from within to outside of the cell. This means that the plasma membrane allows the entry of some substances while preventing the movement of some other substance

Blood is a fluid connective tissue that consists of plasma, blood cells and platelets. It circulates throughout our body delivering oxygen and nutrients to various cells and tissues. It makes up 8% of our body weight. An average adult possesses around 5-6 litres of blood.

Blood is responsible for the following body functions:

Fluid Connective Tissue

Blood is a fluid connective tissue composed of 55% plasma and 45% formed elements including WBCs, RBCs, and platelets. Since these living cells are suspended in plasma, blood is known as a fluid connective tissue and not just fluid.

Provides oxygen to the cells

Blood absorbs oxygen from the lungs and transports it to different cells of the body. The waste carbon dioxide moves from the blood to the lungs and exhaled.

Transports Hormone and Nutrients

The digested nutrients such as glucose, vitamins, minerals, and proteins are absorbed into the blood through the capillaries in the villi lining the small intestine.

The hormones secreted by the endocrine glands are also transported by the blood to different organs and tissues.

Homeostasis

Blood helps to maintain the internal body temperature by absorbing or releasing heat.

Blood Clotting at Site of Injury

The platelets help in the clotting of blood at the site of injury. Platelets along with the fibrin form clot at the wound site

Transport of waste to the Kidney and Liver

Blood enters the kidney where it is filtered to remove nitrogenous waste out of the blood plasma. The toxins from the blood are also removed by the liver.

Protection of body against pathogens

The White Blood Cells fight against infections. They multiply rapidly during the infections.

The Universal Law of Gravitation states that every particle attracts every other particle in the universe with a force that is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.

a=2m/s 

u = 10 m/s, t = 5 sec 

v = u + at

v= 10+2×5

v = 20m/sec

distance = 2 km 

total time = 30 min = 0.5 hour

initial speed = 3km/h for first 1 km

Hence time taken = distance/speed = 1/3 h 

time left = 0.5 - 1/3 = 0.5/3 h

distance left = 1 km

Hence speed at which he should walk the second km wouldeb 1/(0.5/3) = 6 km/h

Average speed of first 
distance = 20 km 
speed = 40 km/h 
time taken  = 20/40 = 1/2 hrs 
2nd time average 
distance = 20 km 
speed = 60 km/h 
time taken by the car is  = 20/60 = 1/3 hrs 
total time taken = t1+t2 = 1/2 +1/3 = 5/6 hrs 
Average speed of the car is = (20+20)/(5/6) 
= 48 km/h 

distance 1 = 10 m
distance 2 = 10 m
time 1 = 2 min = 2×60 = 120 s
time 2 = 3 min = 3×60 = 180 s
Average speed
= (10+10)/(120+180)
= 20/300
= 1/15 m/s
 

The train's maximum speed= 80 km/hr
Average speed = total distance travelled
                          total time taken
The train's average speed= 400km            =  40km/hr
                                         10 hours

ratio of maximum speed to average speed= maximum speed : average speed
                                                                     80km/hr : 40km/hr
                                                                             2:1
=    2:1

Time = 8 hours
distance = 320 km
average speed = total distance covered/ total time taken
= 320/8
= 40
so, the average speed of the bus is 40km/h

D₁ = 7.5×2/60= 0.25km
D₂= 7.5×2/60= 0.25km
Total Distance= 0.25+0.25=0.50km
Total time taken = 2+2+56=60min= 1 HR
Average speed =total distance/ total time
Average speed= 0.50/1= 0.50 km/hr

Carbon dioxide, a waste product, passes across the epithelium of the alveoli to be removed from the body. Striated, columnar and cuboidal epithelium is absent in the lines of alveoli. 

One mole of molecule or ion refers to the quantity in number possessing a mass equal to its atomic or molecular mass in grams. Number of particles present in one mole of any substance is 6.022 X 10²³. This value is called Avogadro number.

So we get 1 mole = 6.022 X 10²³ in number.