That's THERMAL energy, often referred to as "heat".
Answer:
-20,000N
Explanation:
Force (N) = mass (kg) x acceleration (m/s²)
So,
Force = 2000 x -10
= -20,000N (Newtons)
Let F1=Force exerted by the brother (+F1)
F1= Force exerted by the sister (-F2)
Fnet=(+F1) + (-F2)
Fnet= (+F1) + (-F2)
Fnet=F1 - F2
Fnet= (+3N)+(-5N)
Fnet= -2N
-F
towards the sister (-F) (greater force applied)