Determine the minimum force p to prevent the 25-kg rod ab from sliding. the contact surface at b is smooth, whereas the coefficient of static friction between the rod and the wall at a is μs = 0.17.

108.65 N

Explanation:

given,

mass of road = 25 Kg

static friction at A = 0.17

contact force at B

there will a normal force acting at point A i.e Na and a friction force in the vertical direction at Point A i.e. μNa

A horizontal force is acting along point B i.e N_b.

At the middle weight of of the rod will be acting i.e mg at  2 m

diagram attached below shows the forces,

now, taking moment about point B

computing horizontal forces

Na= 108.65 N

now,

computing horizontal forces

P = N_a

P = 108.65 N

hence, P is the contact force at point B

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

1/0.14nm = 10^10/1.4 a lot