Suppose a clay model of a koala bear has a mass of 0.235 kg and slides on ice at a speed of 0.720 m/s. It runs into another clay model, which is initially motionless and has a mass of 0.305 kg. Both being soft clay, they naturally stick together. What is their final velocity (in m/s)

The value is  

Explanation:

From the question we are told that

     The mass  of the first  model is  

      The sliding speed is  

       The mass of the second model is  

Generally from the law of momentum conservation w have that

Here is the velocity of the second model and given that it is  motionless at it initial state the value will be  

 So  

=>              

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.