Page 1 :
5, , 8. A large force acting for a short interval of time is called impulsive force., , Give two examples for impulsive force., , b. How is the impulse of a force calculated?, , ‘c. What is the unit of impulse?, , Ans.a. Kicking football, Hammering on a nail,, , b. Impulse = Impulsive force x time = Fxt_ Ns, , ‘9, Which is the law that is also known as law of inertia?, , Ans. First law., , 10, Newton's second law of motion helps to measure force,, , ‘a. State the law, b, Write down equation for finding out the force using this equation., , ‘c. When a force was applied to an object of mass 5 kg, it got an acceleration of 4 mvs* . Calculate the force, applied on the body., , Ans.a.The rate of change of momentum of a body is directly proportional to the unbalanced extemal force, ‘acting on it., , bc Force = mass x acceleration = ma, , c. F=ma=5x4=20N., , 11. Which law of motion is made in use of Rocket launching? State the law., , ‘Ans, Newton's third law:- To every action there is an equal and opposite reaction., , 12. A person cannot push aside a car by standing on a slippy surface. What might be the reason?, ‘Ans, Because he doesn’t get reactive force from slippy surface as there is no friction,, , 3. Velocity ~ time graph a moving object of mass 2 kg is, , , , , , 4. Find momentum of the object at 4" second., bb. What is the acceleration of the object during first four, seconds?, «Calculate the force applied then., . Find out the displacement of the object during 6, seconds., ‘Ans.a.P =my = 2x2=4 kgm/s, b. Acceleration= (v ~ u)/(t~ ti) = (2-0)(40), Force, F = ma=2x0.5 = 1N Time(s) —>, 4. Displacement = Area of the triangle OAB, M4 bh= % xGx2 = 6m, 14.Itis the centripetal force which keep up the object in uniform circular motion in its circular path., «a. Give an example for uniform circular motion,, b. What is the direction of centripetal force?, ‘c-Write down the expression for centripetal force and specify the variables in it., ‘Ans.a. The movement of the tip of the hands of a watch., b. To the centre along the radius,, c. Centripetal force Fe=mv‘/r —m—mass , v— velocity, radius of the path., 15, What is called the acceleration produced by the centripetal force? What is its direction?, ‘Ans.i. Centripetal acceleration. It direcs towards the centre of the circular path along the radius., 16, Loaded heavy vebicle cannot be stopped abruptly by applying brake. Why?, Ans. The mass of loaded vehicles will be large. So inertia of motion (tendency to continue its motion) will be, greater., 17."In the absence of an extemal force, the total momentum of a system is a constant” Identify the law., Ans, Law of conservation of momentum,, 18, What are the forces and their directions on a brick kept at rest on a horizontal surface, How do the forces, relate?, ‘Ans, i. Weight acting vertically downward ii. Upward normal reaction from the surface., ‘These forces are equal and opposite,, , , , , , Velocity (rvs)
