Question

Please help me i dont get it

Answer 1

The answers are:

39:

a - 1 mile

b - 0 miles

40:

$a=-4\frac{m}{s^{2} }$

41:

$Displacement=3.60 miles\\Distance=5 miles$

Why?

Solving 39:

To answer the questions, we need to remember that distance and displacement are different things. Distance refers to the total "ground" covered during motion, while displacement refers to how far is the object/body from its starting point.

So,

39:

a - the total distance traveled corresponds to the length of the track which is 1 mile.

b - The displacement is equal to 0 because they finished at the starting point,  the distance between the starting and the finishing point is equal to 0.

40:

We can solve the problem using one of the given equations:

$a=\frac{v_f-v_i}{t}$

Since we know all the information, we just need to substitute it into the equation:

$a=\frac{v_f-v_i}{t}\\\\a=\frac{2\frac{m}{s} -16\frac{m}{s} }{3.5s}=\frac{-14\frac{m}{s} }{3.5s}\\\\a=-4\frac{m}{s^{2} }$

So, the car's acceleration was -4m/s2 (the car was reducing its speed)

41:

We can solve the problem using one of the given equations (Pythagorean Theorem):

$c^{2}=a^{2}+b^{2}$

$Displacement=\sqrt{(3mi(North))^{2}+(2miles(East))^{2}}\\\\Displacement=\sqrt{9+4}=\sqrt{13mi^{2}}=3.60miles$

The distance will be:

$Distance=3mi+2mi=5miles$

Have a nice day!