Question

a motorcycle of mass 180kg running eith a speed of 50 m/s is stopped in 10s on applying brakes.Calculate the constant retardation of the motorcycle and the retarding force exerted by the brakes?
class 9​

Answer 1

Answer:

Retardation = 5 m/s²

Retarding force = 900 N

Explanation:

$\underline{\bigstar\:\textsf{Given:}}$

• Mass (m) = 180 kg
• Initial velocity (u) = 50 m/s
• Final velocity (v) = 0 m/s (As brakes were applied)
• Time (t) = 10 s

$\underline{\bigstar\:\textsf{To\:find:}}$

• Retardation (-a) = ?
• Retarding force exerted (-F) = ?

$\underline{\bigstar\:\textsf{Solution:}}$

We are given with initial and final velocities and time, Now we have to find the retardation or -ve acceleration.

We remember, $\blue{\sf{Acceleration(a)\:=\:\dfrac{v\:-\:u}{t}}}$

Here, v = Final velocity

$\:$ u = Initial velocity

$\:$ t = time

$\:$ a = Acceleration

$\implies\:\sf{a\:=\:\dfrac{0\:-\:50}{10}}$

$\implies\:\sf{a\:=\:\dfrac{-50}{10}}$

$\implies$ a = -5 m/s²

$\underline{\underline{\sf{\therefore\:Retardation\:is\:5\:m/s^2}}}$

(or acceleration = -5 m/s²)

By second law of motion we knows, $\orange{\sf{Force(F)\:=\:Mass(m)\:\times\:Acceleration(a)}}$

Now, we know the acceleration i.e, -5 m/s² and the mass of motorcycle is given so just put all the given values for retarding force.

➳ F = 180 × -5

➳ F = -900 N

➳ $\underline{\underline{\sf{\therefore\:Retarding\:force\:is\:900\:Newton}}}$

"Note: Where the word retarding or retardation comes that means something is negative not positive."