Answer: A and C (i took the test)
Explanation: Hope this helps:)
Answer:
5 ms-2
Explanation:
F = ma
F = 100N
m = 20kg ( you should make sure the unit is kg before you answer the question)
100 = 20a
a = 100÷ 20
a = 5 ms-2
During convection of air currents, cool air sinks. <em>(b)</em>
Answer:

Explanation:
We know that the tangent function relates the angle of the right triangle that forms the hot air balloon rising:

Differentiating (1) with respect to time, we get:

since x is a constant value. Replacing:

It depends whether or not the object in moving relative or not to the reference point, for instance imagine a void where there were no dimensions, but there was an object. You can’t tell if the object is moving or not without a reference point.