Answer:
Change in velocity and direction over a specific period of time.
Explanation:
In physics, acceleration can be defined as the rate of change of the velocity of an object with respect to time.
This simply means that, acceleration is given by the subtraction of initial velocity from the final velocity all over time.
Hence, if we subtract the initial velocity from the final velocity and divide that by the time, we can calculate the acceleration of an object.
Mathematically, acceleration is given by the equation;


Where,
a is acceleration measured in 
v and u is final and initial velocity respectively, measured in 
t is time measured in seconds.
Hence, the types of changes in motion that cause acceleration is a change in velocity and direction over a specific period of time.
Answer: (d)
Explanation:
Given
Mass of object 
Speed of object 
Mass of object at rest 
Suppose after collision, speed is v
conserving momentum

Initial kinetic energy

Final kinetic energy

So, it is clear there is decrease in kinetic energy . Thus, energy decreases and velocity becomes 2 m/s.
Answer:
Because it can easily resist air resistance.
Explanation:
Since air resistance is not negligible, the crumpled paper will reach the ground first because it can easily resist air resistance surrounding it compare to the un-crumpled one that will be influenced by the air thereby causing the un-crumpled paper to spend more time in the air