2 10 points

Find the total displacement of each of the motions.

a) You walk 45 m W, then 34 mW

b) You drive 5 km N, then 7 km S

c) You cycle 350 m E, then 800 m W, then 200 m E

d) You fly 850 km N then 850 km S

a) s = 79 m W

b) s = 2 km S

c) s = 250 m W

d) s = 0 km  

Explanation:

We take the following sign convention for the directions:

North (N)  ---> positive

South (S)  ---> negative

East (E) ---> negative

West (W)  ---> positive

a)

45 m W, 34 m W

s = 45 m + 34 m

s = 79 m W

b)

5 km N, 7 km S

s = 5 km - 7 km

s = - 2 km

s = 2 km S

c)

350 m E , 800 m W, 200 m E

s = -350 m + 800 m - 200 m

s = 250 m

s = 250 m W

d)

850 km N, 850 km S

s = 850 km - 850 km

s = 0 km

total distance travelled = 60 miles

total time taken =1.5 hours

average speed = total distance / total time

60 / 1.5

= 40

therefore, average speed = 40 m/h

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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.