Question

A car of mass 500 kg travelling at 36 kilometre per hour is brought to rest over a distance of 40 metre. find the average retardation and average braking force​

Answer 1

Answer:

$\bigstar{Average\:Retardation\:=\:-1.25m/s^{2} }$

$\bigstar{Average\:Force\:=\:-625\:N}$

Step-by-step explanation:

Given:

• Mass of the car(m) = 500kg
• Initial velocity(u) = 36km/hr=10m/s
• Final velocity(v) = 0m/s
• Distance travelled(s) = 40m

To Find:

• Average retardation(a)
• Average braking force(F)

Solution:

Average retardation:

→ By the third equation of motion

     v²-u²=2as

→ Substituting the given datas, we get the value of a

     0²-10²=2×a×40

    a= -1.25m/s²

Here acceleration is negative since it is retardation

Average braking force:

→ By Newton's second law of motion

  F = ma

→ Substituting the given datas, we get

   F = 500× -1.25

  F = -625 N

Notes:

1. Remember to convert all the given datas to their SI units before calculating.
2. The three equations of motion are:

• v=u+at
• s=ut+1/2×a×t²
• v²-u²=2as

Answer 2

Given,

Mass(m) = 500 kg

Initial velocity(u) = 36 km/hr = $\frac{36*1000}{1*60*60}$ = 10m/s

Final velocity(v) = 0 m/s

Distance(s) = 40 m

Now by using 3rd equation of motion

                         v²- u² = 2as

                   or, 0² - 10² = 2 * a * 40

                  or, a = -1.25 m/s²

Therefore, the average retardation is -1.25 m/s²

Again, we know

                       F = MA

                 or, F = 500 * (-1.25)

                or, F = -625 N

Therefore, the average braking force is -625N