A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force \( F = 20 \, \text{N} \) acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take \( g = 10 \, \text{m/s}^2 \)): 
Charles Darwin - was a British naturalist who proposed the theory of biological evolution by natural selection. Darwin derived evolution as "descent with modification," the idea that species change gradually, give rise to new species and share a common ancestor. Darwin had proposed natural selection - the mechanism for evolution. Because resources are short in nature, organisms with heritable traits that favor survival and reproduction will lean to leave more offspring than their peers, causing the traits to rise in frequency over generations. The consequence of natural selection on populations is to become adapted, or increasingly well-suited, to their environments steadily. Natural selection entirely depends on the environment and needs existing heritable variation in a group.
Read More: Types of Natural Selection