Will someone please help me with these Physics questions

Question

When the brakes of a car are suddenly applied, objects not secured fly forward and fall into the floorboard. Which of the following best explains this phenomenon?

a. velocity

b. acceleration

c. force

d. inertia

A piano with a mass of 200 kg is suspended by a rope. What is the gravitational pull on the piano?

F_tension​=m ⋅ gravity

a. 2019 N

b. 1962 N

c. 853 N

d. 1 N

Answer 1

a. inertia. Inertia is the tendency of an object moving with a constant velocity to keep moving with that velocity. So if an object in a car is moving at the same speed as the car and the car suddenly stops the object will want to keep moving forward with the velocity it had (that's why seatbelts are important lol).

b. gravitational force = m g where g = acceleration due to gravity (9.8 m/s/s).

So 200 x 9.8 is the answer here (so 1962 N). And the tension force = mass x acceleration due to gravity.