Hi there!
According to Newton's second law:
∑F = m · a, where:
∑F = net force (N = kgm/s²)
m = mass (kg)
a = acceleration (m/s²)
Rearrange to solve for acceleration:
F/m = a
20N / 4.0kg = 5 m/s²
Mass= density x volume
1.3 kg/m^3 x ( 2.5x4x10) m^3
= 130 kg
When an object does not move even on pushing , static frictional force acts on in opposite direction of the applied force to stop the object from moving. static frictional force is a self adjusting force and it adjust its value according to the applied force if the applied force is smaller than the maximum value of static frictional force. The object starts moving once the applied force on it becomes greater than the maximum static frictional force. hence the statement is true.
That particular group of elements is reffered to as the "Noble Gasses"--a title that comes from the fact that these gases are very "secure" and don't mix well with other elements.
