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.