Question

A car of mass 1200 kg is brought to rest from a speed of 72 km/hr within 80 m. The retarding
force on the car is
(A) 2000 N (B) 3000 N (C) 300 N
(D) 200 N​

Answer 1

Concept Introduction: Newton's law of Motion is the basic of physics.

Given:

We have been Given: Mass of the car is

$1200kg$

$v= 0 \\ u = 72km {h}^{ - 1} = 72 \times \frac{5}{18} = 20m {s}^{ - 2} \\ x = 80m$

To Find:

We have to Find: The retarding

force on the car is

(A) 2000 N (B) 3000 N (C) 300 N

(D) 200 N

Solution:

According to the problem, we know,

$f = ma$

but

${v}^{2} - {u}^{2} = 2as$

therefore,

$a = \frac{( {v}^{2} - {u}^{2}) }{2s} \\ a = \frac{(0 - {20}^{2}) }{2 \times 80} \\ a = - \frac{400}{160} \\ a = - 2.5 m{s}^{ - 2}$

therefore, retarding force is,

$f =1200 \times 2.5 = 3000N$

Final Answer: The Retarding Force is

$3000N$

#SPJ3