Atruck is traveling on a straight stretch of of highway at 120 km/h. the driver spots a police car ahead. if the truck slows with an average acceleration of -4.0 m/s2 how much time does it take to reduce its speed to the legal limit of 96 km/h?

It takes 1.67 seconds to reduce its speed to the legal limit

Explanation:

The main point in this problem is the difference between the units of

the speeds and acceleration

The unit of the speeds is km/hour

The unit of the acceleration is m/sec²

So we must to change the units of the speeds from km/hour to

meter/second

1 km = 1000 m

1 hour = 60 × 60 = 3600 seconds

Then 120 km/hr = m/s

96 km/hr = m/s

To find the time of deceleration (to reduced the speed) we will use:

v = u + at. where u is the initial velocity, v is the final velocity, a is the

acceleration and t is the time

v = 26.67 m/s , u = 33.33 m/s , a = - 4 m/s²

Substitute these values in the rule

26.67 = 33.33 + (- 4)t

Subtract 33.33 from both sides

- 6.66 = - 4t

Divide both sides by - 4

t = 1.67 seconds

It takes 1.67 seconds to reduce its speed to the legal limit

There are not many things that these two microscope types have in common. Both electron and light microscopes are technical devices which are used for visualizing structures that are too small to see with the unaided eye, and both types have relevant areas of applications in biology and the materials sciences. And this is pretty much it. The method of visualizing the structures is very different. Electron Microscopes use electrons and not photons (light rays) for visualization. The first electron microscope was constructed in 1931, compared to optical microscopes they are a very recent invention.