Remember to include your data, equation, and work when solving this problem. a 20.0 kg mass moving at a velocity of + 3.0 m/s is stopped by a constant force of 15.0 n. how many seconds must the force act on the mass to stop it?

4 seconds

Explanation:

We have the following data for this exercise :

A 20.0 kg mass ⇒

A velocity of + ⇒ The module of this vector is the speed ⇒ We have and initial speed of

And a constant force F with a value of 15.0 N ⇒

Let's start finding the acceleration that this force applies over the mass.

We can write the following equation :

Where a is the acceleration over the mass ''m'' due to the force F.

Using this equation we can find the acceleration

The unit N is equivalent to

⇒

Now in order to find the time, we are going to use the following cinematic equation :

Where V is the speed, V0 is the initial speed and t is the time

We want the mass to stop ⇒

We also know the initial speed

(I)

The force must act 4 seconds to stop the mass.

We add a ''-'' in equation (I) because the acceleration is opposite to the movement because it is stopping the mass.

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)

b. a lightning bug, plug of grass, and a worm