Two 100 kg bumper cars are moving toward each other in opposite directions. Car A is moving at 8 m/s and Car B at −10 m/s when they collide head–on. If the resulting velocity of Car B after the collision is 8 m/s, what is the velocity of Car A after the collision?

The velocity of Car A after the collision is 10 [m/s] in opposite direction to its original movement

Explanation:

In order to solve this problem we must use the principle of conservation of linear momentum, which is defined as the product of mass by Velocity.

P = m*v

where:

P = momentum [kg*m/s]

m = mass [kg]

v = velocity.

We have to study the moment before the collision and the moment after the collision, the moment before the collision will be taken to the left of the equal sign and the moment after the collision will be taken to the right of the equal sign.

ΣPbefore = ΣPafter

(m1*v1) + (m2*v2) = (m1*v3) + (m2*v4)

where:

m1 = m2 = 100 [kg]

V1 = velocity of car A = 8 [m/s]

V2 = velocity of car B = - 10 [m/s]

V4 = velocity of car B after the collision = 8 [m/s]

(100*8) - (100*10) = (100*V3) + (8*100)

V3 = -10 [m/s]

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.