Question

a train travelling at a speed of 90 km per hour. brakes are applied so as to produce a uniform acceleration of -0.5 ms^-2. find how far the train will go before it is brought to rest?

Answer 1

Convert 90 Km/Hr to m/s.
90 × 5/18 = 25 m/s.

Here U = 25 m/s, A= 0.5 m/s^2 and the train is being brought to rest hence V = 0 m/s.
Using the formula,
V = U + AT
0 = 25 + (-0.5)×T
0 = 25 - 0.5T
Transposing 0.5 T to left
0.5T = 25
Transposing 0.5 to right
T = 25/0.5 = 50 sec.

Answer 2

u = 90 kmh^-1

= 25 ms^-1

a = -0.5 ms^-2

v = 0

s = ?

Using 3rd equation of Motion

${\boxed{\bigstar{{v^{2} = u^{2} + 2as}}}}$

0 = (25)^2 + 2(-0.5)s

s = 625 m