A boy throws rocks with an initial velocity of 12 m/s [down] from a 20 m bridge into a river. Consider the river to be at a height of 0 m. Draw a velocity-time and position-time graph. Use up as positive and ignore air resistance.

a. 48 salads were bought on Wednesday

b. 42 chickens were bought on Thursday

c. 39 cheese were bought on Friday

Step-by-step explanation:

Given

------- M -- T - W -- T -- F−−−−−−−M−−T−W−−T−−F

Cheese ----- 50 -- 45 - 52 - 47 --39

Salad -------- 61 -- 44 - - 48 - 38 -- 51

Chicken ---- 53 -- 46 - - 39 - 42 -- 52

First, it should be noted that the horizontal data represent the row while the vertical data represent the column.

Having said that, the solution is as follows:

Solving (a): Second Row, Third column

The data at the second row are:

------- M -- T - W -- T -- F−−−−−−−M−−T−W−−T−−F

Salad -------- 61 -- 44 - - 48 - 38 -- 51

The data at the third column is then limited to:

------------------W

Salad -------- 48

So the number at this position implies that: 48 salads were bought on Wednesday

Solving (b): Third Row, Fourth column

The data at the second row are:

------- M -- T - W -- T -- F−−−−−−−M−−T−W−−T−−F

Chicken ---- 53 -- 46 - - 39 - 42 -- 52

The data at the fourth column is then limited to:

------------------- T

Chicken ---- 42

So the number at this position implies that: 42 chickens were bought on Thursday

Solving (c): First Row, Fifth column

The data at the first row are:

------- M -- T - W -- T -- F−−−−−−−M−−T−W−−T−−F

Cheese ----- 50 -- 45 - 52 - 47 --39

The data at the fifth column is then limited to:

------------------F

Cheese ----- 39

So the number at this position implies that: 39 cheese were bought on Friday

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.