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STD . 6th Sub:Science, 10 .Force and Type of Force, Summative Evaluation, Question and Answer, Q.1. Fill in the blanks, (1) Force has to be applied to change the direction of a moving object., (2) When an elephant drags a wooden log over the land, the forces that are applied on the log are muscular force, gravitational force and frictional force., (3) A ball was set rolling on a large table. If it's motion is to be changed, a force will have to be applied on it., (4) The force of friction always acts against the motion., Q. 2. Match the following:, Q. 3. One or more forces are acting in the following examples. Name them., (1) An object falling from a tall building., Ans. Gravitational force., (2) An aeroplane flying in the sky., Ans. Mechanical force, muscular force, frictional force. gravitational force., (3) Squeezing sugarcane juice with a squeezer, Ans. Mechanical force, muscular force, frictional force., (4) Winnowing food grains., Ans. Muscular force, gravitational force., Q. 4. Explain in your own words giving one example each :, (1) Muscular force:, Ans. The bones and muscles of our body help us to perform movements. Muscular force is used to perform all these movements. The force applied with the help of muscles is called muscular force. E.g. a man who pulls the handcart uses muscular force to perform the work. The coolie lifting the luggage uses muscular force., (2) Gravitational force:, Ans. Earth pulls all the objects towards it. This force is called gravitational force of gravity, e.g. The rocket that takes off from the ground, applies the mechanical force against the gravitational force. All the things on the earth, stay on the earth due to gravitational force., (3) Mechanical force:, Ans. The force applied with the help of machines is called mechanical force. Some machines are used with the help of muscular force, while some machines work on electricity or fuel. These machines are automatic. Machines help us to carry out tasks with ease and speed., e.g washing machine, food processor, water pump., (4) Electrostatic force:, Ans. Electrostatic force is produced by the materials which develop static electricity on them. eg. Due to electrically charged materials like ebonite, plastic, rubber this force is produced., (5) The force of friction / Frictional force:, Ans. Frictional force is created by friction. Two surfaces rub against each other and produce frictional force. e.g. the brakes used in stopping a running vehicle work on the frictional force. The footpaths and slopes of the walk ways have rough surface to create more frictional force, so that people do not slip and fall as they walk., (6) Magnetic force:, Ans. The force exerted by a magnet is called magnetic force. Magnetic force is used in many gadgets such as doorbell, huge cranes that lift loads., Q. 5. Why? (Give reasons) :, (1) Machines are oiled from time to time., Ans. Machines are used to save our energy and time. The machines working on mechanical force should work efficiently. If they are not oiled, the frictional force may be created between the surfaces of this machine. If frictional force is more it will slow down the speed and efficiency of the machine, therefore, machines are oiled from time to time., (2) An object thrown upwards comes down after reaching a point., Ans. An object thrown upwards goes up due to muscular force. At one point during its ascent the muscular force becomes zero. The gravitational force then starts operating on thus object. It pulls this object down. Thus, an object thrown upwards comes down after reaching a point., (3) The ramp at a railway station has a rough surface., Ans. There should be more frictional force created on the ramp of the railway station. If the surface is smooth and slippery, there will be no frictional force. People using ramp in a hurry will slip and fall down easily. In order to avoid this and keep people safe. the ramp at a railway station has a rough surface., Q. 4. In what way are we different?, (1) Muscular force and mechanical force:, (2) The Force of friction and Gravitational force, Q. 5. Write answers to the following questions in your own words: H) What are the things that can be done by applying force?, Ans. Force can be applied to almost all things. Lifting, pulling, riding a bicycle, pushings load, squeezing or bending something, driving vehicles, using different machines, and almost all the day-to-day activities are done by applying force., (2) What is meant by weight?, Ans. The gravitational force acting on an object is called the weight of that object., (3) Which machines run on muscular force?, Ans. Handcart, plough, ores of boat, bullock cart, horse carriage, bicycle, grinding stone, etc. are the machines that run on muscular force., (4) Use your brain power!, Which forces are acting upon an aeroplane taking off into the sky?, Ans. When an aeroplane takes off. It uses mechanical force. The pilot uses muscular force. The weight or gravitational force pulls down the aeroplane. This opposes the lift created by air flowing over the wing. This is a frictional force. Thrust is generated by the propeller this is a mechanical force and opposes drag caused by air resistance to the airplane,