Question

If a car is traveling westwards with a constant speed of 20 m/s, what is the resultant force acting on it? (Ans:Zero)

Answer 1

according to Newton's 2nd law of motion , force is defined as when a body moves in variable velocity , it posses acceleration and force is the product of mass and acceleration.
e.g., Force = mass × acceleration.

but in case of constant velocity , acceleration will be zero. obviously force will be zero.
coz , F = mass × 0 = 0

hence, resulted force acting on it is zero.

Answer 2

Hi,

Yes ,the answer of your question is ZERO.

The Reason:

According to Newton's law:
For any moving object ,if direction and speed are constant than acceleration is Zero.

If acceleration is Zero ,than force would definitely be zero.

F = ma
here a is acceleration and m is mass.

secondly,you studied that rate of change of velocity with respect to time is acceleration,here speed is constant(20 m/s)
So,no change in speed.

$a = \frac{dv}{dt} = \frac{v2 - v1}{t2 - t1} \\ \\ let \: t2 = 10 \: sec \\ t1 = 5 \: sec \\ v2 and \: v1 = 20 \: m {s}^{ - 1} \\ a = \frac{20 - 20}{10 - 5} = \frac{0}{5} = 0$

so, Force would be zero from formula F= ma.

hope you understand well.