Newton's first law of motion is sometimes called the law of inertia. When the forces acting on an object are balanced, the object is either at rest or moving with a constant velocity. Unbalanced forces can cause an object to accelerate or decelerate. Unbalanced forces can also cause an object to change direction.
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Answer:

the answer is A.
Explanation:
Using the laws of newton:
∑F = ma
where ∑F is the sumatory of forces acting in the system, m the mass and a the acelertion of the system.
Then, if the block is moving with constant velocity, its aceleration is equal to 0, so:
∑F = m(0)
∑F = 0
It means that:
F -
= 0
where F is the force applied and
is the friction force. Replacing the value of F, we get:
310N -
= 0
Finally, solving for
:

Answer:
Explanation:
From the given information:
the car's momentum = momentum of the truck
∴
(a) 816 kg × v = 2650 kg × 16.0 km/h
v = (2650 kg × 16.0 km/h) / 816 kg
v = 51.96 km/hr
(b) 816 kg × v = 9080 kg × 16.0 km/h
v = (9080 kg × 16.0 km/h) / 816 kg
v = 178.04 km/hr