Question

An automobile travelling with a speed of 60km/hr then brake is applied to stop it within a distance of 20m. If the car is going twice as fast ie 120km/hr the stopping distance will be?

Answer 1

Best Answer:  Initial Velocity U = 60 km/h = 16.66 m/s  

using V² - U² = 2as  

given s=20 m and V=0 m/s  

=> -(16.66)² = 2*a*20  

=> Acceleration(a)= -6.93 m/s²  

NOW IN 2ND CASE: U = 120 km/h = 33.33 m/s and V=0 m/s  

using V² - U² = 2as  

=> -(33.33)² = 2*(-6.93)*s  

=> s= 80.15 m

PRECAUTIONARY MEASURES:

If tested in real life it would not perform to the mathematical answer. Heat buildup in brakes reduces their efficiency and heat would rise continuously during the test. Whether the tires skidded for part of the test would change the distance, too. Also, if the car deviated from the straight path. If the anti-lock mechanism activated the distance would increase significantly and most recent cars have that system.