UPSC Prelims 2003 · General Studies
Question 26: Science and Technology
Consider the following statements: A four-wheel vehicle moving on a sharp circular path at high speed will
- 1.Overturn about its outer wheels.
- 2.Overturn about its inner wheels.
- 3.Skid outwards.
- 4.Skid inwards.
Which of these statements are correct?
AnswerThe answer is (a).
On a sharp bend at high speed, the vehicle needs a large inward force to follow the curve, and friction can supply only so much. If friction is not enough, the car skids outwards, away from the centre of the curve. Because the car's weight acts at a height above the road, the outward inertial effect also gives a turning moment about the outer wheels, so it can overturn about them. It does not skid inwards or pivot on its inner wheels.
- 1. The outward effect gives a moment about the outer wheels, which can tip the car over them.
- 2. The pivot is the outer wheels, not the inner wheels.
- 3. If friction cannot provide the inward force, the car slides outwards.
- 4. Skidding is away from the centre of the curve, never towards it.
How you could have got this
- If you were sure statement 1 is correct, (b) and (c) go: each of them leaves 1 out.
What you needed to know: The outward effect gives a moment about the outer wheels, which can tip the car over them.
- Then, if you were sure statement 3 is correct, (d) goes: it leaves 3 out.
What you needed to know: If friction cannot provide the inward force, the car slides outwards.
Only (a) is left. You didn’t need statements 2 or 4.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Correct: overturning about the outer wheels and skidding outwards.
- (b) The inner wheels lift off the road; the car does not pivot about them, and it does not skid inwards.
- (c) Overturning about the inner wheels is wrong.
- (d) Skidding inwards is wrong.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.