A racecar accelerates along a straight track. It reaches 160 km/hr when it is 0.4 km from the start. It maintains the same speed until it is 1.6 km from the start. What is the displacement of the car during the time that it goes 160 km/hr?

0.799km

Explanation:

First we need to get the acceleration diring the first part of the journey. According to equation of motion, v² = u² + 2as where;

v is the final velocity = 160km/hr

= 160000/3600 = 44.4m/s

u is the initial velocity = 0km/hr = 0m/s

S is the distance covered= 0.4km = 400m

44.4² = 0² + 2(400)a

1971.36 = 800a

a = 1971.36/800

a = 2.46m/s²

Since the car accelerates for 2.46m/s² during the first part of the journey, we can get the time taken by the car during this period using

v = u + at

44.4 = 0 + 2.46t

t = 44.4/2.46

t = 18seconds

Displacement if the car during this period will be gotten using the formula change in velocity = displacement/time

Displacement = change in velocity×time = 44.4 × 18 = 799.2m

= 0.799km

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s

f is prop to m1xm2 double m1 double force