Question

A truck is moving with speed of 54 km/h. Truck’s driver applied brakes suddenly and brings the truck to rest in 5 sec. What is the average retarding force on truck, if the mass of the truck and driver is 400 kg,will be






How 54*5/18m/s how 18 is come ​

Answer 1

Answer:

We know

Force= Mass×Acceleration

here,mass=400kg

But a=?

given

initial velocity,u= 54 km/h= 54×5/18= 15m/s

final velocity,v= 0 (turned rest)

time, t = 5 sec

we know

$a = \frac{v - u}{t} \\ a = \frac{0 - 15}{5} \\ a = - 3$

therefore the retardation is -3m/s²

and now,to calculate force

Force= Mass × Acceleration

Force= 400 × -3

Force= -1200

the negative sign implies that force acted against the object

Therefore the Force acted is 1200N