Acar of mass 550 kg is moving at a speed of 1.5 m/s. a man pushes the car,
increasing the speed to 3.2 m/s. how much work did the man do?
a. 2816 j
b. 3435 j
c. 2197 j
d. 4123 j

C. 2197 J

Explanation:

The work done = Energy change

The work done by man = Kinetic energy change of the car

Kinetic energy is the energy possessed by a moving object solely due to its motion.

You can get the K.E. of an object using the equation,

K.E. =  (1/2)mv²

So you get,  

The work done by man =  K.E. change of the car

                                       = (1/2)×550×(3.2)²  - (1/2)×550×(1.5)²

                                       = 2197.25 J

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.