Question

A particle moving with an initial velocity of 5 metre per second is subjected to a uniform acceleration of -2.5 metre per second square find the displacement in the next 4 seconds​

Answer 1

Explanation:

displacement is given by...

s = ut + (1/2)a t^2

where, u - initial speed

a - acceleration

t - time

here, a = -2.5 m/sq-sec

t = 4 s

u = 5 m/s

so,

s = 5×4 - (1/2)× 2.5 × 4×4 = 20 - 20 = 0

displacement = 0

that means, it comes to rest at some point of time.

so, let final velocity = v = 0

s = (v^2 - u^2)/(2a) = - 5×5 / (- 2×2.5) = 5 m

so, displacement when the velocity becomes zero = 5 m

Now,

if the acceleration comes due to braking system,

then,

displacement = 5 m

if acceleration is due to some constant force acting continuously (even after v= 0), in opposite direction of initial motion,

then, displacement = 0