A racing car has uniform acceleration of 4 ms–2.
[question] Question. A racing car has uniform acceleration of 4 ms–2. What distance will it cover in 10 s after start ? [/question] [solution] Solution: Given Initial velocity, $\mathrm{u}=0$ Acceleration, $a=4 \mathrm{~ms}^{-2}$ Time, $\mathrm{t}=10 \mathrm{~s}$ Distance covered, $\mathrm{s}=?$ We know, s $=$ ut $+\frac{1}{2} \mathrm{at}^{2}$ $\mathrm{s}=0 \times 10+\frac{1}{2} \times 4 \times(10)^{2}$ $=0+200=200 \mathrm{~m}$ Therefore, distance covered $=200 \mathrm{~m}$. [/solution]...
Read More →A trolley, while going down an inclined plane,
[question] Question. A trolley, while going down an inclined plane, has an acceleration of 2 cms–2. What will be its velocity 3 s after the start ? [/question] [solution] Solution: Given, initial velocity, $\mathrm{u}=0$; final velocity, $\mathrm{v}=?$ Time, $\mathrm{t}=3 \mathrm{~s}$ Acceleration, $\mathrm{a}=2 \mathrm{cms}^{-2}$ We know that, $\mathrm{v}=\mathrm{u}+\mathrm{at}$ or $\mathrm{v}=0+2 \times 3=6 \mathrm{cms}^{-1}$ Therefore, final velocity $=6 \mathrm{cms}^{-1}$. [/solution]...
Read More →Why are traits acquired during the
[question] Question. Why are traits acquired during the life-time of an individual not inherited? [/question] [solution] solution: Acquired traits are those traits which are acquired by the organism in its life time. In these traits, genes of germ cells is not changed so they are not passed into next generation. [/solution]...
Read More →A train is travelling at a speed of 90 kmh–1.
[question] Question. A train is travelling at a speed of 90 kmh–1. Brakes are applied so as to produce a uniform acceleration of – 0.5 ms–2. Find how far the train will go before it is brought to rest. [/question] [solution] Solution: Given, initial speed of train, $\mathrm{u}=90 \mathrm{~km} \mathrm{~h}^{-1}=90 \times \frac{5}{18}=25 \mathrm{~ms}^{-1}$ Final speed, $\mathrm{v}=0 \mathrm{~ms}^{-1}$, Acceleration, $\mathrm{a}=-0.5 \mathrm{~ms}^{-2}$, Distance covered, $\mathrm{s}=$ ? Using the re...
Read More →Form the pair of linear equations in the following problems and find their solutions (if they exist) by any algebraic method
[question] Question. Form the pair of linear equations in the following problems and find their solutions (if they exist) by any algebraic method (i) A part of monthly hostel charges is fixed and the remaining depends on the number of days one has taken food in the mess. When a student A takes food for 20 days she has to pay Rs. 1000 as hostel charges whereas a student B, who takes food for 26 days, pays Rs. 1180 as hostel charges. Find the fixed charges and the cost of food per day. (ii) A frac...
Read More →A bus starting from rest moves with a uniform acceleration
[question] Question. A bus starting from rest moves with a uniform acceleration of $0.1 \mathrm{~ms}^{-2}$ for 2 minutes. Find (a) the speed acquired. (b) the distance travelled. [/question] [solution] Solution: Given Initial speed of bus, $\mathrm{u}=0 \mathrm{~ms}^{-1}$ Final speed of bus, $v=$ ? $\mathrm{a}=0.1 \mathrm{~ms}^{-2}, \mathrm{t}=2 \mathrm{~min}=120 \mathrm{~s}$ $\mathrm{s}=$ ? (i) We know, $\mathrm{v}=\mathrm{u}+\mathrm{at}$ or $\mathrm{v}=0+0.1 \times 120=12 \mathrm{~ms}^{-1}$ (i...
Read More →What are the different ways in which individuals
[question] Question. What are the different ways in which individuals with a particular trait may increase in a population? [/question] [solution] solution: Individuals with a particular trait may increase in a population as a result of the following: (i) Natural selection: When that trait offers some survival advantage. (ii) Genetic drift: When some genes governing that trait become common in a population. (iii) When that trait gets acquired during the individual's lifetime. [/solution]...
Read More →How is the sex of the child determined in human beings?
[question] Question. How is the sex of the child determined in human beings? [/question] [solution] solution: In female there are two $X$ means $(X X)$ chromosomes but in case of males these are one $X$ and other Y means (XY). [/solution]...
Read More →What is the quantity which is measured by
[question] Question. What is the quantity which is measured by the area occupied below the velocity-time graph ? [/question] [solution] Solution: Distance is the quantity which is measured by the area under velocity time graph. [/solution]...
Read More →A man with blood group A marries a woman with
[question] Question. A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not? [/question] [solution] solution: No, because there is no information about the blood group of all the progenies.Blood group A can be genotypically AA or AO. [/solution]...
Read More →How do Mendel’s experiments show
[question] Question. How do Mendel’s experiments show that traits are inherited independently? [/question] [solution] solution: In dihybrid cross when a plant with round and yellow seeds were crossed with a plant with wrinkled and green seeded plant in F2 generation he obtained four combinations instead of two parental varieties, this is possible only when the factors of each character is free to move with any other factor of other character. This is called law of independent assortment. [/solut...
Read More →What can you say about the motion of an object if its speed-time graph
[question] Question. What can you say about the motion of an object if its speed-time graph is a straight line parallel to the time axis ? [/question] [solution] Solution: he object may be in uniform motion. [/solution]...
Read More →How do Mendel's experiments show
[question] Question. How do Mendel's experiments show that traits may be dominant orrecessive? [/question] [solution] solution: Mendel found that in his monohybrid and dihybrid cross out of a pair of contrasting trait in F1 generation only one trait is expressed and other remain hidden, the expressed trait is called dominant and the hidden trait is called recessive. [/solution]...
Read More →What can you say about the motion
[question] Question. What can you say about the motion of an object whose distance time-graph is a straight line parallel to the time axis ? [question] [solution] Solution: The object is stationary. [solution]...
Read More →What is the nature of the distance time graphs
[question] Question. What is the nature of the distance time graphs for uniform and non-uniform motion of an object? [question] [solution] Solution: The distance-time graph for uniform motion is a straight line, not parallel to the time axis. The distance-time graph for non-uniform motion is not a straight line, it can be a curve or a zigzag line [solution]...
Read More →How does the creation of variations in a
[question] Question. How does the creation of variations in a species promote survival? [/question] [solution] solution: Creation of variation may be suitable for a population to fight against some new change in environment while those which do not have this variation will not be able to fight with such changing conditions and will die. [/solution]...
Read More →A train starting from a railway station
[question] Question. A train starting from a railway station and moving with uniform acceleration attains a speed of 40 kmh–1 in 10 minutes. Find its acceleration. [/question] [solution] Solution: Given $t=10 \mathrm{~min}=10 \times 60=600 \mathrm{~s}$ Initial speed of train, $\mathrm{u}=0 \mathrm{~ms}^{-1}$ Final speed of train $\mathrm{v}=40 \mathrm{~km} \mathrm{~h}^{-1}=40 \times \frac{5}{18}=11.1 \mathrm{~ms}^{-1}$ Now acceleration is given by the relation $\mathrm{a}=\frac{\mathrm{v}-\mathr...
Read More →If a trait $\mathrm{A}$ exists in $10 \%$ of a population of an asexually
[question] Question. If a trait $\mathrm{A}$ exists in $10 \%$ of a population of an asexually reproducing species and a trait $\mathrm{B}$ exists in $60 \%$ of the same population, which trait is likely to have arisen earlier? [/question] [solution] solution: The trait $\mathrm{B}$ has arisen earlier since it in $60 \%$ population while trait $\mathrm{A}$ is merely in $10 \%$ which is newly arisen and not spread to large number. [/solution]...
Read More →Solve the following pair of linear equations by the substitution and cross-multiplication methods:
[question] Question. Solve the following pair of linear equations by the substitution and cross-multiplication methods: 8x + 5y = 9, 3x + 2y = 4 [/question] [solution] Solution: By substitution method, 8x + 5y = 9 ...(i) 3x + 2y = 4 ...(ii) From (ii), we get $x=\frac{4-2 y}{3}$ Substituting x from (iii) in (i), we get $8\left(\frac{4-2 y}{3}\right)+5 y=9$ = 32 – 16y + 15y = 27 = 5 = y Substituting y = 5 in (ii) we get 3x + 2(v) = 4 = 3x = – 6 = x = – 2 Hence, x = – 2, y = 5 By cross multiplicati...
Read More →A bus decreases its speed from 80 km
[question] Question. A bus decreases its speed from 80 km h–1 to 60 km h–1 in 5 s. Find the acceleration of the bus. [question] [solution] Solution: Given $t=5 \mathrm{~s}$ Initial speed of bus $\mathrm{u}=80 \mathrm{~km} \mathrm{~h}^{-1}=80 \times \frac{5}{18}=22.2 \mathrm{~ms}^{-1}$ Final speed of the bus $\mathrm{v}=60 \mathrm{~km} \mathrm{~h}^{-1}=60 \times \frac{5}{18}=16.6 \mathrm{~ms}^{-1}$ Now acceleration is given by the relation $\mathrm{a}=\frac{\mathrm{v}-\mathrm{u}}{\mathrm{t}}=\fra...
Read More →What could be the reasons for
[question] Question. What could be the reasons for adopting contraceptive methods ? [/question] [solution] solution: Contraceptive methods are adopted for one or more of following reasons- (i) To maintain the population size by preventing unwanted children. (ii) To maintain the distance between two children and to plan the family size. (iii) To prevent from sexually transmitting diseases. (iv) Good reproductive health. [/solution]...
Read More →When will you say a body is in
[question] Question. When will you say a body is in (i) Uniform acceleration ? (ii) Non uniform acceleration ? [question] [solution] Solution: (i) A body is in uniform acceleration when it moves in a straight line and equal changes of velocity take place in equal intervals of time. (ii) A body is said to be possessing non-uniform acceleration when unequal changes in velocity take place in equal intervals of time....
Read More →How does reproduction help in providing stability
[question] Question. How does reproduction help in providing stability to populations of species ? [/question] [solution] solution: By reproduction variations are added in population, which may be suitable for some changing conditions of environment. In case of adversity of environment some of member survives and prevents the entire population from vanishing off. [/solution]...
Read More →During an experiment a signal from a spaceship reached the ground station
[question] Question. During an experiment a signal from a spaceship reached the ground station in five minutes. What was the distance of the space ship from the ground station ? The signal travels at the speed of light that is, $3 \times 10^{8} \mathrm{~m} / \mathrm{s}$. [/question] [solution] Solution: Let the distance between the spaceship and the ground station be 's'. Then, $\mathrm{s}=\mathrm{v} \times \mathrm{t}$ where, $\mathrm{v}=$ speed of signal $=3 \times 10^{8} \mathrm{~m} / \mathrm{...
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