Question

A car of a mass of 140kg traveling at a speed of 36 km/h is brought to rest over a distance of 30 meters. Find a) Average retardation​

Answer 1

Answer:

Explanation:

Force F = mass m × acceleration a

Retarding Force F = mass m × deceleration (-a)

100 km/h = (100×1000)/(60×60) m/s

To find deceleration, use formula v^2 = u^2 + 2as where v = final velocity 0 m/s, u = initial velocity (100×1000)/(60×60) m/s, a = deceleration , s = distance 40 m.

0^2 = (100×1000/60×60) + 2a(40) => a = -(100×1000/60×60)(1/(2×40)) = -25/72 m/s^2.

Average Braking Force F = mass × deceleration = 1 000 × (-25/72) = -347.2 N.

Answer 2

Explanation:

u=36km/h

=36×5/18

=10m/sec

v=0m/s

s=30m

${v}^{2} = {u}^{2} + 2as \\ {0}^{2} = {10}^{2} + 2a30 \\ 0 = 100 + 60a \\ a = 100 \div 60 \\ a = 6 {m \: persec}^{2}$

a=-6m/sec square