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
Answer:
28 m/s^2
Explanation:
distance, s = 14 m
time, t = 2 - 1 = 1 s
initial velocity, u = 0 m/s
Let a be the acceleration.
Use third equation of motion


a = 28 m/s^2
Thus, the acceleration is 28 m/s^2.
The answer is binary star system