I. Four alternatives are given to each of the following incomplete statement\/ question. Choose the right answer.<\/p>\n
Question 1.
\nWhich one of the following is not correct – Action and reaction
\na) act on the same body
\nb) are equal
\nc) are opposite
\nd) act on different bodies
\nAnswer:
\nd) act on different bodies<\/p>\n
Question 2.
\nIf the forces acting on an object are balanced then
\na) the object will be accelerated
\nb) the object will be in motion
\nc) the object will have zero acceleration,
\nd) the object loses its shape
\nAnswer:
\nc) the object will have zero acceleration<\/p>\n
Question 3.
\nThe correct way to write S.I. unit of force is
\na) Newtons
\nb) newton
\nc) newtons
\nd) newton
\nAnswer:
\nb) newton<\/p>\n
II. Fill in the blanks<\/p>\n
Question 1.
\nInertia of an object is proportional to its ……………
\nAnswer:
\nmass<\/p>\n
Question 2. Question 3. Question 4. Question 5. III. Answer the following.<\/p>\n Question 1. Question 2. b) Mass m = 1 kg Question 3. Question 4. Question 5. Question 6. IV. Give a reason for the following.<\/p>\n Question 1. Question 2. Question 3. V. Solve the problems.<\/p>\n Question 1. Question 2. Question 1. Question 2. Question 3. Question 4. Question 5. Question 6. Question 7. Question 8. Question 9. Question 10. Question 11. Question 12. Question 13. <\/p>\n","protected":false},"excerpt":{"rendered":" Karnataka Board Class 8 Science Chapter 9 Force and Newton’s Laws of Motion KSEEB Class 8 Science Chapter 9 Textual Questions & Answers I. Four alternatives are given to each of the following incomplete statement\/ question. Choose the right answer. Question 1. Which one of the following is not correct – Action and reaction a) …<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts\/4832"}],"collection":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/comments?post=4832"}],"version-history":[{"count":0,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts\/4832\/revisions"}],"wp:attachment":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/media?parent=4832"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/categories?post=4832"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/tags?post=4832"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nThe SI unit of momentum is ………..
\nAnswer:
\nkg ms-1<\/sup><\/p>\n
\nTo cause acceleration in an object, the necessary factor is unbalanced ……….
\nAnswer:
\nforce<\/p>\n
\nNewton\u2019s first law of motion is also called law of …………..
\nAnswer:
\ninertia<\/p>\n
\nThe suitcases kept in a moving bus move forward when the brakes are applied suddenly this is due to ……….
\nAnswer:
\ninertia<\/p>\n
\nIn a tug of war game if the two teams exert equal forces none of the team wons. Why?
\nAnswer:
\nIn a tug of war game, if the two team exert equal forces none of the team wons since it maintain the tug in the equilibrium position or in the same state as the forces are balanced forces.<\/p>\n
\nWhich of the following has greater momentum?
\na) An object of mass 2 kg moving with uniform velocity of 2 ms-1
\n<\/sup>b) An object of 1 kg mass moving with uniform velocity of 3 ms-1<\/sup>
\nAnswer:
\na) Mass = 2 kg
\nVelocity = 2 ms-1<\/sup>
\nMomentum M = mass \u00d7 velocity
\n= 2 x 2 = 4 kg ms-1<\/sup><\/p>\n
\nVelocity v = 3 ms-1<\/sup>
\nMomentum M = mass \u00d7 velocity
\n= 1 x 3 = 3 kg ms-1<\/sup>
\nTherefore object of mass 2 kg moving with uniform velocity of 2 ms-1<\/sup> has greater momentum.<\/p>\n
\nWhich of the following has greater inertia?
\na) 50 paisa coin
\nb) one rupee coin
\nc) five rupee coin
\nAnswer:
\nc) five rupee coin has greater inertia.<\/p>\n
\nState any two illustrations for Newton\u2019s third law of motion.
\nAnswer:<\/p>\n\n
\nDistinguish between balanced and unbalanced forces.
\nAnswer:<\/p>\n\n
\n
\n
\nState newton\u2019s second law of motion in the terms of momentum.
\nAnswer:
\nThe acceleration given to a body by a force applied to it is directly proportional to the force and in the same direction of the force and inversely proportional to the mass of the body. F = ma<\/p>\n
\nIt is dangerous to get down from a moving bus even if the bus is moving slowly.
\nAnswer:
\nThe person getting down from a moving bus runs for a certain distance in the direction of the bus due to inertia which may lead to an accident. Therefore it is dangerous to get down from a moving bus.<\/p>\n
\nAn athlete in a long-jump runs a distance before taking the leap.
\nAnswer:
\nIt is possible to jump a longer distance if the athlete runs a distance before taking the leap. This is because the acceleration given to a body by a force applied to it is directly proportional to the force. When a body moves, it wilt continue to move with some velocity when no force acts on it. According to this principle, if an athlete runs from a distance, he\/she can jump a longer distance with the same force.<\/p>\n
\nUsually, a fielder in a cricket match takes a catch by moving his hands in the direction of the motion of a cricket ball.
\nAnswer:
\nUsually, a fielder in a cricket match takes a catch by after taking the moving his hands in the direction of the motion Of cricket ball. Due to inertia, the ball continues in its state of uniform motion in a straight line in the same direction. So the impact on the hands will be less.<\/p>\n
\nCalculate the force required to change the velocity, of an object of mass 8kg from 4 ms-1 to 6 ms-1 in 2 seconds.
\nAnswer:
\nData :
\nm = 8 kg
\nu = 4 ms-1<\/sup>
\nv = 6 ms-1<\/sup>
\nt = 2 sec
\na = ?
\nF = ?
\nSolution:
\na = \\(\\frac { v-u }{ t }\\)
\n= \\(\\frac { 6-4 }{ 2 }\\)
\n= \\(\\frac { 2 }{ 2 }\\) = 1 ms-1<\/sup>
\nF = ma
\n=8 \u00d7 1 = 8 kg ms-2 <\/sup>= 8 N<\/p>\n
\nA force of 25 newtons is applied on an object of mass 10 kg moving with a velocity of 5 ms-1<\/sup> If the object gains a velocity of 10
\nms-1<\/sup>. Calculate the time interval.
\nAnswer:
\nData :
\nF = 25 N
\nm = 10 kg
\nu = 5 ms-1<\/sup>
\nv = 10 ms-1<\/sup>
\na = ?
\nt = ?
\nSolution :
\nF = ma
\nma = F
\n10 a = 25
\na = \\(\\frac { 25 }{ 10 }\\) = 2.5 ms-2
\n<\/sup>v = u + at
\n10 = 5 + 2.5 t
\n2.5 t = 10 \u2013 5
\n2.5 t = 5
\nt = \\(\\frac {5 }{ 2.5 }\\) = 2 sec<\/p>\nKSEEB Class 8 Science Chapter 9 Additional Questions & Answers<\/h3>\n
\nDefine force? Mention the effect of force.
\nAnswer:
\nForce is a physical quantity that changes the state of the rest of a body or that changes the velocity of a body. Effects of force applied on an object can<\/p>\n\n
\nWhat are unbalanced forces?
\nAnswer:
\nThe effect of force will be observed when an unbalanced force acts on an object. Unbalanced forced acting on an object, changes its speed or direction of motion.<\/p>\n
\nWhat are balanced forces?
\nAnswer:
\nIf two or more forces acting on the same object keep the object in equilibrium position or in the same state, then the forces are balanced forces.<\/p>\n
\nWhat is meant by Frictional force?
\nAnswer:
\nFriction is the opposing force which comes, whenever there is relative motion between two bodies.<\/p>\n
\nWhat is meant by inertia?
\nAnswer:
\nThe tendency of the objects to remain at rest or state of motion when no forces act on them is called inertia.<\/p>\n
\nState Newton\u2019s first law of motion.
\nAnswer:
\nEverybody continues in its state of rest or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it.<\/p>\n
\nWhat are the SI units of mass and acceleration?
\nAnswer:
\nSI unit of mass is kg SI unit of acceleration is ms-2<\/p>\n
\nCalculate the force required to change the velocity of an object of mass 4 kg from 2 ms-2<\/sup> to 4 ms-2<\/sup> in one second.
\nAnswer:
\nSolution
\nF = ma
\nm = 4 kg
\na = 2 ms-2<\/sup>
\nF = ?
\nF = 4 kg x acceleration
\nF = 4 x 2
\n= 8 kg ms-1<\/sup> or 8 newton or 8 N.<\/p>\n
\nAn object of mass 10 kg is moving with an initial velocity of 2 ms-1<\/sup>. To make it come to rest in one second, what should be the unbalanced force?
\nAnswer:
\nSolution,
\ninitial velocity = 2 ms-1<\/sup>
\nvelocity at rest = 0 ms-1<\/sup>
\ntime interval = 1 second
\nmass m = 10 kg
\nchange in velocity in one second or acceleration
\n= \\(\\frac { 0-2 }{ 1 }\\) = 2 ms-1<\/sup>
\nF = ma
\nF = 10 \u00d7 2
\n= 20 kg ms-2<\/sup>\u00a0or -20 newton or-20 N.
\nThe negative sign tells us that the force exerted is opposite to the direction of motion.<\/p>\n
\nAn object of mass 20 kg is moving with an initial velocity of 2 ms-1<\/sup>. If its velocity changes to 4 ms-1<\/sup> in one second. What should be the force acting on it? What will be the direction of the motion?
\nAnswer:
\nSolution
\nF = ma
\nm = 20 kg
\na = \\(\\frac { 4-2 }{ 1 }\\) = 2 ms-1
\n<\/sup>F = 20 x 2 = 40 newton or 40 N.
\nThe object continues to move in the same direction as the force applied is in the same direction.<\/p>\n
\nState the conservation of momentum
\nAnswer:
\nConservation of momentum states that the total momentum of a system conserved when the net external force acting on the system is zero.
\nmv + MV = 0 or mv = \u2013 MV<\/p>\n
\nState Newton\u2019s third law of motion.
\nAnswer:
\n\u201cTo every action there is always an opposed and equal reaction or The mutual actions of two bodies upon each other are always equal and directed in opposite direction.<\/p>\n
\nA bullet of mass 25 g is fired from a rifle of mass 2 kg. Imagine that no other forces are acting on the system. If the bullet travels with a velocity of 2 ms-1<\/sup>, what will be the velocity of the recoil of the rifle?
\nAnswer:
\nMomentum of the rifle = momentum of the bullet
\nMass of the rifle \u00d7 velocity of recoil = mass of the bullet \u00d7 Velocity of the bullet
\n2 \u00d7 velocity of recoil = \\(\\frac { 25 }{ 1000 }\\) \u00d7 2
\n2 \u00d7 velocity of recoil = \\(\\frac { 1\\times 2 }{ 40 }\\) = \\(\\frac { 1 }{ 2 }\\)
\nvelocity of recoil = \\(\\frac { 1 }{ 2 }\\) \u00d7\u00a0 \\(\\frac { 1 }{ 20 }\\) =\u00a0 \\(\\frac { 1 }{ 40 }\\) =0.0025 ms-1<\/sup><\/p>\n KSEEB Solutions for Class 8 Science<\/a><\/h4>\n