(p = mv). Hence, with the forward movement of the bus, the luggage tends to remain at its original position and ultimately falls from the roof of the bus. Given, mass of the bullet (m) = 10g (or 0.01 kg), Initial velocity of the bullet (u) = 150 m/s, Terminal velocity of the bullet (v) = 0 m/s. Therefore, the leaves that are weakly attached to the branch fall off due to inertia whereas the leaves that are firmly attached to the branch remain attached. Yes. If a person jumps from a height on a concrete surface he gets hurt. 10. 2. Your email address will not be published. Answer: Momentum of two bodies before collision is equal to the momentum after collision. Question 13. We also do not move because the force of reaction acting on us (due to our pushing the truck) is less than force of friction between us and the road. This is why the dust comes out of the carpet when beaten. How does a karate player breaks a slab of ice with a single blow? A force can do 3 things on a body Assume that there is no external unbalanced force working in the horizontal direction. Answer: Question 1. Question 1. When we are travelling in a vehicle and sudden brakes are .applied we tend to fall forward. 1N = 1kg m/s2 When the carpet is beaten with a stick, the stick exerts a force on the carpet which sets it in motion. 8. Is it possible for the object to be travelling with a non-zero velocity? Saksham saw his karate expert friend breaking a slate. (b) To every action there is an equal and opposite reaction, both act on different bodies. However, Rahul’s suggestion that the change in the momentum is the same contradicts the law of conservation of momentum. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. This frictional force eventually stops the ball. (d) Car suffers more damage than the truck, as acceleration of car is more, its velocity falls to zero in a shorter time and consequently, its momentum changes in a shorter time. What is the momentum of an object of mass m, moving with a velocity v? How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Answer: While moving in a bus our body is in motion. Question 2. Answer: As per given table initial speed of the object is zero. But when an unbalanced force is applied by the engine to change the direction of motion of the motorcar. What decides the rate of change of momentum of an object? 3. (c) no unbalanced force acts on it A truck starts from rest and rolls down a hill with a constant acceleration. 30 Days Study Plan for IBPS RRB Officer Scale 1 and Office Assistant Prelims. Therefore, the total momentum post the collision is also 10 kg.m.s-1. (c) both have different inertia (d) both have different momentum But the upper part of our body continues to be in motion and hence we fall in forward direction due to inertia of motion. Answer: When the tree’s branch is shaken vigorously the branch attain motion but the leaves stay at rest. Answer: Given, mass of the objects (m1 and m2) = 1.5kg, Initial velocity of the first object (u1) = 2.5 m/s, Initial velocity of the second object which is moving in the opposite direction (u2) = -2.5 m/s, When the two masses stick together, the resulting object has a mass of 3 kg (m1 + m2). Is it constant, increasing, decreasing, or zero? (c) a five-rupees coin and a one-rupee coin? Answer: It is a push or pull on an object that produces acceleration in the body on which it acts. With what velocity would the two move together? Therefore, the student’s logic is correct. A batsman hits a cricket ball which then rolls on a level ground. Comment on these suggestions. (c) Newton ( (d) Newton-meter Answer: Question 1. Answer: A body of mass 20 kg will have more inertia. However, the inertia of the leaves attached to the branch resists the motion of the branch. Question 1. Inertia: The natural tendency of an object to resist a change in their state of rest or of uniform motion is called inertia. What is her velocity as the cart starts moving? How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Answer: Question 4. Applying the relation, Question 2. Why do fielders pull their hand gradually with the moving ball while holding a catch? Question 5. (a) mass of the body (b) velocity of the body Also, calculate the velocity of the combined object. Answer: The natural tendency of an object to resist a change in their state of rest or of uniform motion is called inertia. What is momentum? Class V students were playing cricket with the cork hall in the school campus. What is balanced force? Why is it advised to tie any luggage kept on the roof of a bus with a rope? Object of mass m, is moving along a straight line with an initial velocity ‘u’, It is uniformly accelerated to velocity v in time ‘t by the application of force, Give 3 examples in daily life which shows inertia. Formulae Handbook for Class 9 Maths and ScienceEducational Loans in India. State Newton’s III law of motion. Force and Laws of Motion Class 9 Numericals Force and Laws of Motion Class 9 Numericals Solved – Solutions. Forces A, B, Since the truck has a very high mass, the static friction between the road and the truck is high. (d) all of these Three examples of inertia in daily life are: Answer: The force applied on the card due to flicking changes the inertia of the card but the coin resist a change and stay at the rest i.e. 4. Determine the velocity of the second object. However, the inertia of the leaves in attached to the branch resists the motion of the branch. (d) there is no unbalanced force on the ball, so the ball would want to come to rest. The S.I. Two persons manage to push a motorcar of mass 1200 kg at a uniform velocity along a level road. From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m/s. Fielder giving a swing while catching a ball is an example of Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Question 2: According to the third law o motion, when we pushed on an object, the object pushes back on us with an equal and opposite force. With what force does each person push the motorcar? NCERT Class 9 Science Chapter 9 Force and laws of motion is covered under unit 3 Motion, Force and Work. NCERT Solutions offer comprehensive answers to all the questions to help students in their preparations. Answer: While catching a. fast moving cricket ball, a fielder on the ground gradually pulls his hands backwards with the moving ball. Name the factor on which the inertia of the body depends. Kiran’s suggestion is correct. (c) there is a force on the ball opposing the motion. (b) lighter ball is dropped faster than heavier ball Initial momentum of the car = m × u = (1200kg) × (25m/s) = 30,000 kg.m.s-1, Final momentum of the car = m × v = (1200kg) × (5m/s) = 6,000 kg.m.s-1, Therefore, change in momentum (final momentum – initial momentum) = (6,000 – 30,000) kg.m.s-1, External force applied = mass of car × acceleration = (1200kg) × (-5 ms-2) = -6000N, Therefore, the magnitude of force required to slow down the vehicle to 18 km/hour is 6000 N. NCERT Solution Class 9 Science Chapter 9 explains what is a force and its application with various examples. The simple and easily understandable method is followed in NCERT solutions to make students knowledgeable of concepts.