Answer:
The average force exerted on the window due to two snowballs is 6 N
Explanation:
Given:
Mass of snowballs
Kg
Velocity of snowball 
For finding the average force,
Force is equal to the change in momentum,

Here, final velocity is zero so we write,

Where
sec

N
Above value of force is due to one ball, but here given in question there are two ball,

N
Therefore, the average force exerted on the window due to two snowballs is 6 N
Answer:
Explanation: Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object. As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased.
Answer:
2. The metal surface exerts less frictional force because there are fewer bumps and irregularities on it than there are on the concrete.
Explanation:
Frictional force is a force that is exerted between two surfaces in contact with each other. Frictional force always opposes the direction of relative motion of the two surfaces: for instance, for a ball moving along a surface, the force of friction exerted by the surface on the ball points opposite to the direction of motion of the ball.
The magnitude of the frictional force for a ball moving on a flat surface is given by

where
is the coefficient of friction
m is the mass of the ball
g is the acceleration of gravity
The value of
depends on the type of surface involved. In particular, a smooth surface has a smaller value of
, while a rough surface will have a bigger value. In this case, we are comparing a smooth metal surface with concrete: since the metal surface has fewer bumps and irregularities than concrete, it has a smaller value of coefficient of friction, so it exerts less frictional force than concrete.