KPK 9th Class Physics Chapter 3 Dynamics Short Questions Answers
KPK 9th Class Physics Chapter 3 Dynamics Short Questions with answers are combined for all 9th class(Matric/ssc) Level students.Here You can prepare all Physics Chapter 3 Dynamics short question in unique way and also attempt quiz related to this chapter.Just Click on Short Question and below Answer automatically shown. After each question you can give like/dislike to tell other students how its useful for each.
Class/Subject: 9th Class Physics
Chapter Name: Dynamics
Board: All KPK Boards
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KPK 9th Class Physics Chapter 3 Dynamics Short Questions Answers
Why does dust fly off, when a hanging carpet is beaten with a stick?
When hanging carpet is beaten with a stick dust particles fly off due to inertia. When the carpet is beaten with a stick the carpet moves forth and back while the dust particle maintains its position due to inertia. Consequently the dust particles get removed from the carpet.
If your hands are wet and no towel is handy, you can remove some of the excess water by shaking them. Why does this work?
That property of a body due to which it resists a charge in its state of res or of uniform motion is known as inertia.
When we are shaking hands, our hands come into wants to be at rest and try to remain at rest due to inertia. Consequently, these drops are removed from our hands.
Why a balloon filled with air move forward, when its air is released?
When air is released from the balloon, the balloon moves in the forward direction.
According to the law of conservation of momentum, the momentum of the air released in the backward direction must be equal to the momentum of the balloon in the forward direction. The total momentum of the balloon must equal to zero.
Now when air is released, it rushes out with great momentum in the backward direction. Now to conserve momentum, the balloon moves forward with the same momentum.
Why does a hose pipe tend to move, backward when the fireman directs a powerful stream of water towards fire?
When fireman is directing a powerful steam of water from a hose pipe towards fire, the water shoots out from the pipe in forward direction which is action on water. In reaction the water pushes the pipe in backwards direction. In other wards we can say that, in order to conserve momentum when water is released from the pipe, the pipe moves in the backward direction.
Your car is stuck in wet mud. Some student on their way to class see your predicament and help out by sitting on the trunk of your car to increase its traction why does this help?
When the car is stuck in wet mud, the friction between tyres and wet mud decreases, due to which the car can not come out of wet mud. We know that the frictional force is directly proportional to weight of the object.
f ∝ w
when the students sit on the car trunk this increase the weight of the car trunk and thus increase the frictional force between tyrea and mud. In this way the car comes out of the mud.
How does friction help you walks? Is it kinetic friction or static friction?
We would be unable to walk, if there was no friction between the soles of our shoes and ground. It is because when we push the ground in backward direction, the ground reacts back according to Newton’s 3rd law motion only on account of friction. Therefore friction is the necessary force which help us to walk on the ground.
This is static friction because the contact part of our shoes is momentarily at rest with the ground.
The parking brake on a car causes the rear wheels to lock up. What would be the likely consequence of applying the parking brake in a car that is in rapid motion?
When we drive a car on the road with a fast speed and applying the parking brake (Hand brake) the rear two wheels of car will be lock up, while two front wheels of a car are in motion due to inertia. These two front wheels try to maintain their state of motion. As the two rear wheels of a car are locked up, so the car will skid.
Why is the surface of a conveyor belt made rough?
The surface of conveyor belt is made rough to increase its force of friction. For rough surface irregularities are large due to which the area of contact increases and thus friction also increases. As a result, the things lying on the belt remain safe from falling down.
Why does a boatman tie his boat to a pillar before allowing the passengers to step on the river bank?
When the passenger form the boat move towards the river bank pushes the boat with their feet in the backward direction. According to Newton’s 3rd law of motion the reaction of boat is in opposite direction but when boat is tied with pillar it cannot over and hence the passenger move out from boat easily.
In a uniform circular motion, is the velocity constant? Is the acceleration constant? Explain.
When an object moves in a circle then speed of object is uniform but the direction of the object is changes at very instant therefore velocity of the object is not uniform. In circular motion acceleration is produces due to change in direction of motion. This acceleration is directed toward the center if the circle and this acceleration is constant.
Above equation shows that acceleration is constant in uniform circular motion.
You tie a brick to the end of rope and whirl the brick around you in a horizontal circle. Describe the path of the brick after you suddenly let go of the rope?
If the brick is tied to the end of the rope and whirled in a circle. The tangent centripetal force is supplied by our hand through the rope to the brick the brick exerts a centrifugal force on our hand through the rope when the rope is suddenly let go the brick moves away along the tangent to the circle.
Why is the posted speed for a turn lower than the speed limit on most highways?
The posted speed for a turn is lower then the speed limit on highways because moving along a turn require centripetal force which is provided by the friction between the tures and road with high speed this friction is smaller and the required centripetal force could not be provided and the vehicle may escape the turn and driven away from the road.