Question

A car with a mass of 1.2 x 10^3 kilograms starts from rest and attains a speed of 20 meters/seconds in 5 seconds. What net force acted on the car to cause that acceleration?
A.) 3.0 x 10^2 Newton’s
B.) 6.0 x 10^2 Newton’s
C.) 1.2 x 10^3 Newton’s
D.) 4.8 x 10^3 Newton’s
E.) 1.2 x 10^4 Newton’s

Answer 1

The mass of the car [m] = 1.2×10^3 kg.

The initial speed of car[u]= 0 m/s

The final speed of car [v]= 20 m/s

We are asked to calculate the force required to increase the speed from 0 to 20 m/s.

The momentum of a substance is defined as product of mass and velocity.

Mathematically momentum p=m×v   [Here m is the mass]

From Newton's second law we know that-

                       $F=\frac{dp}{dt}$

                       $F=\frac{mv-mu}{t}$     [here t is the time]

                              $= \frac{1200*20-0}{5}\ N$

                              $=\frac{24000}{5} \ N$

                              $=4800\ N$

                              $= 4.8*10^{3} \ N$      [ANS]

Hence the correct answer to the question is C.