While an object is moving at a constant 20 m/s, a 5 N forcepushes the object to the left. At the same time, a 5 N force ispushing the object to the right. What will the object'svelocity be after 10 seconds?

20m/s.

Explanation:

Remember the second Newton's law:

F = a*m

This is:

The net force acting on an object is equal to the mass of the object times the acceleration of the object.

In this case, we have a force of 5N pushing the object to the right.

We also have a force of 5N pushing the object to the left.

These forces act on opposite directions.

Then the net force will be equal to the difference of these forces, this is:

F = 5N - 5N = 0N

Then the net force is 0N, then we have:

0N = m*a

0N/m = 0m/s^2 = a

This means that the acceleration of the object is 0, then the velocity of the object does not change.

This means that if the object was moving at a constant velocity of 20m/s, the velocity of the object will still be equal to 20m/s. (because the net force acting on the object is zero)