What nuclide is formed when 90Sr undergoes β
− decay?
1. 90Rb
2. 86Kr
3. 89Sr
4. 94Zr
5. 90Y

Y-90

Explanation:

In a decay, the nucleus emits an electron and an electron antineutrino, thus causing the atomic number of the nucleus to increase by one while its mass number remains the same. Therefore, the new nucleus after the decay is

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

490 n

f=125n a=2.5m/s2