A 1580kg car is travelling at a speed of 15.0m/s.What is the magnitude of the horizontal net force that is required to bring it to a halt in a distance of 50.0m

Question

magnitude in force

Answer 1

I suggest you first use a kinematic relationship to get the acceleration, then use Newton's 2nd law to get the force.

 

Kinematic relationship to get acceleration:

 

v_f² - v_i² = 2ax

 

v_f = final speed = 0 m/s (comes to a full stop)

v_i = initial speed = 15.0 m/s

x = distance over which the accelerating force acts to bring about a full stop = 50.0 m

a = acceleration

 

a = -v_i²/(2x) = -(15.0 m/s)² / [2(50.0 m)] = -2.25 m/s²

 

The negative sign indicates it is a deceleration.

 

Newton's 2nd law:

 

F = ma = (1580 kg)(-2.25 m/s²) = -3555 N

 

The negative sign indicates the force is opposing the direction of motion.  The magnitude of the force is

 

|F| = 3555 N