Problems&Exercises

A beam of 168-MeV nitrogen nuclei is used for cancer therapy. If this beam is directed onto a 0.200-kg tumor and gives it a 2.00-Sv dose, how many nitrogen nuclei were stopped? (Use an RBE of 20 for heavy ions.)

(a) If the average molecular mass of compounds in food is 50.0 g, how many molecules are there in 1.00 kg of food? (b) How many ion pairs are created in 1.00 kg of food, if it is exposed to 1000 Sv and it takes 32.0 eV to create an ion pair? (c) Find the ratio of ion pairs to molecules. (d) If these ion pairs recombine into a distribution of 2000 new compounds, how many parts per billion is each?

Calculate the dose in Sv to the chest of a patient given an x-ray under the following conditions. The x-ray beam intensity is
1.50 W/m2 , the area of the chest exposed is
0.0750m2 , 35.0% of the x-rays are absorbed in 20.0 kg of tissue, and the exposure time is 0.250 s.

(a) A cancer patient is exposed to
γ rays from a 5000-Ci
60Co transillumination unit for 32.0 s. The
γ rays are collimated in such a manner that only 1.00% of them strike the patient. Of those, 20.0% are absorbed in a tumor having a mass of 1.50 kg. What is the dose in rem to the tumor, if the average
γ energy per decay is 1.25 MeV? None of the
βsize 12{β} {} s from the decay reach the patient. (b) Is the dose consistent with stated therapeutic doses?

Large amounts of
65Zn are produced in copper exposed to accelerator beams. While machining contaminated copper, a physicist ingests
50.0 μCi of
65Zn . Each
65Zn decay emits an average
γ -ray energy of 0.550 MeV, 40.0% of which is absorbed in the scientist’s 75.0-kg body. What dose in mSv is caused by this in one day?

Naturally occurring
40K is listed as responsible for 16 mrem/y of background radiation. Calculate the mass of
40K that must be inside the 55-kg body of a woman to produce this dose. Each
40K decay emits a 1.32-MeV
β , and 50% of the energy is absorbed inside the body.

(a) Background radiation due to
226Ra averages only 0.01 mSv/y, but it can range upward depending on where a person lives. Find the mass of
226Ra in the 80.0-kg body of a man who receives a dose of 2.50-mSv/y from it, noting that each
226Ra decay emits a 4.80-MeV
α particle. You may neglect dose due to daughters and assume a constant amount, evenly distributed due to balanced ingestion and bodily elimination. (b) Is it surprising that such a small mass could cause a measurable radiation dose? Explain.

The annual radiation dose from
14C in our bodies is 0.01 mSv/y. Each
14C decay emits a
β– averaging 0.0750 MeV. Taking the fraction of
14C to be
1.3×10–12N of normal
12C , and assuming the body is 13% carbon, estimate the fraction of the decay energy absorbed. (The rest escapes, exposing those close to you.)

If everyone in Australia received an extra 0.05 mSv per year of radiation, what would be the increase in the number of cancer deaths per year? (Assume that time had elapsed for the effects to become apparent.) Assume that there are
200×10−4size 12{"200" times "10" rSup { size 8{ - 4} } } {} deaths per Sv of radiation per year. What percent of the actual number of cancer deaths recorded is this?

acleration is vectr quatity it is found in a spefied direction and it is product of displcemnt

bhat

its a scalar quantity

Paul

velocity is speed and direction. since velocity is a part of acceleration that makes acceleration a vector quantity. an example of this is centripetal acceleration. when you're moving in a circular patter at a constant speed, you are still accelerating because your direction is constantly changing.

Josh

acceleration is a vector quantity. As explained by Josh Thompson, even in circular motion, bodies undergoing circular motion only accelerate because on the constantly changing direction of their constant speed. also retardation and acceleration are differentiated by virtue of their direction in

fitzgerald

respect to prevailing force

fitzgerald

What is the difference between impulse and momentum?

Manyo

Momentum is the product of the mass of a body and the change in velocity of its motion.
ie P=m(v-u)/t (SI unit is kgm/s). it is literally the impact of collision from a moving body.
While
Impulse is the product of momentum and time.
I = Pt (SI unit is kgm) or it is literally the change in momentum

fitzgerald

Or I = m(v-u)

fitzgerald

the tendency of a body to maintain it's inertia motion is called momentum( I believe you know what inertia means) so for a body to be in momentum it will be really hard to stop such body or object..... this is where impulse comes in.. the force applied to stop the momentum of such body is impulse..

what impulse is given to an a-particle of mass 6.7*10^-27 kg if it is ejected from a stationary nucleus at a speed of 3.2*10^-6ms²? what average force is needed if it is ejected in approximately 10^-8 s?