The question is a little confusing. An electromagnetic wave is radiation. One doesn’t emit the other. Take another look at the question and write it again please.
Answer:
In bringing you to a halt, the sand and the water exert the same impulse on you, but the sand exerts a greater average force
Explanation:
D is the correct answer, assuming that this is the special case of classical kinematics at constant acceleration. You can use the equation V = Vo + at, where Vo is the initial velocity, V is the final velocity, and t is the time elapsed. In D, all three of these values are given, so you simply solve for a, the acceleration.
A and C are clearly incorrect, as mass and force (in terms of projectile motion) have no effect on an object's motion. B is incorrect because it is not useful to know the position or distance traveled, unless it will help you find displacement. Even then, you would not have enough information to use a kinematics equation to find a.
Answer:
Approximately 
, assuming that the acceleration of this ball is constant during the descent.
Explanation:
Assume that the acceleration of this ball, 
, is constant during the entire descent.
Let 
denote the displacement of this ball and let 
denote the duration of the descent. The SUVAT equation 
would apply.
Rearrange this equation to find an expression for the acceleration, , of this ball:
.
Note that 
and 
in this question. Thus:
.
Let 
denote the mass of this ball. By Newton's Second Law of Motion, if the acceleration of this ball is , the net external force on this ball would be 
.
Since 
and 
, the net external force on this ball would be:
.
