Question

A motor car moving at a speed of 72 km/h cannot come to a stop in less than 3.0sec while for a truck this time interval is 5.0 sec on a highway the car is behind the truck both moving at 72km/hrs the truck gives a signal that it is going to stop at emergency. at what distance the car should be from the truck so that it does not bump onto the truck​

Answer 1

Answer:

Car will not bump Truck in anyways

Explanation:

A motor car moving at a speed of 72 km/h cannot come to a stop in less than 3.0sec while for a truck this time interval is 5.0 sec on a highway the car is behind the truck both moving at 72km/hrs the truck gives a signal that it is going to stop at emergency. at what distance the car should be from the truck so that it does not bump onto the truck​

A motor car moving at a speed of 72 km/h cannot come to a stop in less than 3.0sec

if Car stops in 3 sec then

Then retardation using V = U + at

U = 72 km/Hr = 72000/3600 = 20 m/s

0 = 20 + a3

=> a = -20/3 m/s²

Distance Covered using V² - U² = 2aS

=> 0 - 20²  = 2(-20/3)S

=> S = 30 m

Car Travels for 30 m

Truck Stops in 5 sec

Retardation    0 = 20 + a5

=> a = -4 m/s²

Velocity after 3 sec = 20 - 4*3 = 8 m/s

Distance covered  

8² - 20² = 2(-4)S

=>  S = 42 m

as Truck Covers more distance than Car

=>  Car will not bump Truck in anyways