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IIT-JEE Mechanics Free Notes > Foundation series > Conceptual questions.

As a prelude to the launch of our free IIT JEE PHYSICS  ULTIMATE NOTE SERIES  ( UNS ) ,we begin with some conceptual questions in Mechanics.These are meant to test whether the student has grasped the practical aspects of the theory involved. The answers will be provided shortly.The calibre of the questions is at the foundation ( basic ) to the advanced level.

  1. Asteroids are continously moving through space for millions of years.What keeps them moving ?
  2. When tearing paper, a sharp jerk is more effective than a slow force. Why is this so ?
  3. Whiplash is a kind of neck injury which occurs, if a car hits from behind the car at rest in which you are in.Account for this using Newton’s first law.Also,how does a head-rest help you from whiplash ?
  4. A ball thrown up,stops moving up at a particular height.Is it in equilibrium at this height ?
  5. A hockey puck slides across a ice feild at constant speed. Is it in equilibrium ?
  6. On a body at rest,what is correct …. no force is acting or, no net force is acting ? Explain.
  7. A heavy book placed on a table is pushed up by the table.If that’s the case,why doesn’t the book rise up ?
  8. The Earth travels faster than 100,000 kilometres per hour around the sun,but we aren’t swept off the earth.Give reasons
  9. You are tossing a coin straight up,when riding a train.Where does the coin land a) when the train is moving uniformely along a straight line track b) when the trains slows and  c) when the train is turning ?
  10. An airplane flying due east,and returns dues west on return trip.Flying in one direction,it flies with the rotation of the earth and in the opposite direction,against the earth’s rotation.Neglecting air resistance,the time of flight is equal either way..why is this so ?
  11. The greatest time a human can stay in air ( hang time ) when jumping is mostly always less than 1 second.Explain.
  12. Fines are imposed for overspeeding.Is this speed related to average speed or instantaneous speed ?
  13. Is it possible for a vehicle to have velocity towards north and simultaneously have acceleration towards south ? 
  14. You are in a car moving at a specified speed limit and see a car moving towards you at the same speed.How fast is the car approaching you,compared with the speed limit ?
  15. In a straight line motion,how does a speedometer indicate whether the vehicle is accelerating or not ?
  16. Is it possible for a vehicle to reverse it’s direction while maintaining a constant acceleration. Explain.
  17. Is it possible that speed is zero while the acceleration is non-zero ?
  18. Is it possible for an object to have a) constant speed and varying velocity  b) constant velocity and varying speed c) constant speed and acceleration d) constant velocity and acceleration  e) zero speed and acceleration f ) acceleration opposite to the direction of velocity.
  19.  ‘In free fall,air resistance effectively slows a feather than a coin’ – is the statement right ?
  20. How would a speedometer in a feely falling body read the increase in speed with each second of fall ?
  21. If there was no air resistance,would it be dangerous to go outside on a rainy day ? 
  22. A stream of water pouring from a faucet,gets narrower as it falls.Give reasons
  23. You are jumping down from a tree branch.Do you pull upward on Earth ? If so,why is Earth’s acceleration not noticed ?
  24. Greater force can be exerted on the pedals of a bicycle,if one pulls up the handlebars.Explain ?
  25. To climb up using a rope,one has to pull downward on the rope.Why is this so ?
  26. Two astronauts are taking a space walk ,connected by a chord.If one pulls the other towards him,what is the result ?
  27. A bird sitting on a clothesline cause it to sag.When is the tension in the clothesline greater..when the sag is more or less ?
  28. A balloonist climbs a floating balloon,which remains stationary in the air.On climbing,in which direction will the balloon move ?
  29. An aircraft landing,loses both it’s kinetic as well as it’s potential energy.Where does this energy go ?
  30. Does the kinetic energy of an object depend on it’s reference frame ? Give reasons. 
  31. Air bags in cars are meant to reduce injury during collisions.Explain this in terms of impulse and momentum.
  32. Gymnasts practice on thick floor mats. Give reasons ?
  33. Bungee jumpers use elastic cords.Why ?
  34. A person survives a feet-first impact at a speed of around 12 m/s on concrete,15 m/s on soil and 34m/s on water.Why the difference ?
  35. Using the principles of impulse and momentum,explain the need of helicopter blades to deflect air downward ?
  36. We know that it’s more easy to stop a car than a heavy truck ( at same speeds ).Is there a situation where the reverse is true ?
  37. A firefighter finds it difficult to hold a hose ejecting water at high speeds.Explain
  38. Which would hurt more – a punch with bare fists or with a boxing glove ? Give reasons.
  39. Railway coaches are loosely coupled resulting in a time delay when the first coach moves and the last.Why is this so ?
  40. If only an external force can change the velocity of a body, how can the internal force of brakes bring a car to rest ?
  41. Jumping on to a floating boat from land ,one usually lands in water.Explain ?
  42. Is it possible for a swarm of flying objects to have a net momentum of zero ?
  43. A pilot lands in the middle of a frozen lake after bailing out from a damaged aircraft.What must he do to reach the shore by himself ?
  44. Is the law of conservation of momentum voilated when a ball rolls down an incline and gains momentum ?
  45. In a mine,ore is poured on to rail cars causing them to slow.Explain ( ignore friction between the car wheels and the track ).
  46. In an action movie,the hero jumps from a bridge on to a small moving boat with no change in velocity.Is the physics right ?
  47. Three astronauts,all weighing same on earth,plays a game in space,by pushing the third one between the other two.How will this end ?
  48. A sky diver,jumping from a hovering helicopter,finds his momentum increasing.Does this voilate conservation of momentum ? 
  49. A ball is tossed back and forth between two passengers in an airplane in flight. Is the kinetic energy of the ball related to the plane speed ?
  50. The sport of pole vaulting changed when wooden poles were replaced by flexible fibreglass poles. Explain the physics behind the change ?
  51. One gets tired when pushing against a stationary wall,eventhough no work is done on the wall.Why is this so ?
  52. Does the International Space Station ( ISS ) ,floating in space,have gravitational potential energy or kinetic energy ?
  53. Does the string that supports a pendulum bob,do any work on the bob as it swings to and fro ? What about the force of gravity ?
  54. Why must one use a machine,if it can’t multiply work input to acheive greater work output ?                  

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