Which of the following is a positive statement? Question 4 options: A) A humidity level of 90 percent is too high. B) Summer evenings are nice when it cools off to around 70 degrees. C) The temperature is 92 degrees today. D) It is too hot to run outside when the temperature exceeds 80 degrees.

A) A humidity level of 90 percent is too high.

Explanation:

A humidity level of 90% is too high . It reflects real or possible situation .

Atmospheric temperature between 20 -  30 degree makes comfortable weather.  70 or 80 or 90 degree atmospheric temperature is impossible to achieve on the earth in normal case. The maximum temperature upto which

atmospheric temperature has  gone  is 55 degree .

So all the other statements appear to be false.

The change in the linear momentum is 225 kg.m/s and the force exerted on the tennis ball is 22,500 N.

Explanation:

Linear momentum is the measure of a body's motion. Every object that has mass and moves at any velocity has linear momentum. Here are some examples of everyday life: falling balls, launching rockets, driving a car etc.

Now let's attack the problem.

First, we got to write the data down:

We can write the change in linear momentum of the tennis ball as follows:

The ball's momentum is equal to its mass times its velocity. Hence:

Let's set the reference system as positive to left (see picture attached). For that purpose, when the ball bounces back its velocity changes sign.

Now, we are able to plug in the data:

To calculate the exerted force, we must apply the impulse theorem, which states that impulse equals the change in linear momentum of an object. We get:

Hence,

Conclusion: the change in linear momentum is 225 kg . m/s and the exerted force is 22,500 N.

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