Answer:
D. a person pulling a sled.
Explanation:
contact force only occurs when something directly comes in contact with another object.
a. is wrong because that is called magnetic force.
b. gravitational force
c. is an electrical force
It looks blue as it is only reflecting blue light
If it is s-t graph , point is c
if it is v-t graph , point is e
Answer:

Explanation:
We can use the following kinematics equations to solve this problem:
.
Using the first one to solve for acceleration:
.
Now we can use the second equation to solve for the distance travelled by the airplane:
(three significant figures).
Answer:
a.
b.
c. 
Explanation:
Use Gravitational Force:

Use values given to have the results.
b.

Use m as the mass of the Moon. Using values of a. and m you have the answer.
c.

Use M mass of the planet. Use value of a and Mass of Planet.