1) One needs to exert effort to produce motion and stops moving object a) TRUE b) FALSE 2) What stops the ball when you kick it along the ground?  a) ground friction b) gravitational force c) electric force 3) Friction exists due to ___________ of ground.  a) smoothnes  b) roughness c) curveness 4) The larger the _____________ the larger the ____________. a) ball, ground b) roughness, friction c) gravitational force, electric force 5) _______________ is making the floor looks smoother and shinier. It is one way of reducing friction because when roughness decreases, friction decreases too.  a) polishing  b) lubricants c) ball-bearig 6) Applying ______________ such as oil and grease can decrease friction a) lubricants b) water c) sand 7) By using ___________________, we convert sliding friction into rolling friction. This reduces friction.  a) lubricants b) polishing c) ball-bearings  8) Without the ground friction, we wont be able to walk and run.  a) TRUE b) FALSE 9) Due to friction we cannot light a match-stick.  a) FALSE b) TRUE 10) Friction stops or slows down moving vehicles. a) TRUE b) FALSE

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