UDESC – 2019 – EN

UDESC- 2019

The State University of Santa Catarina (UDESC), founded in 1965, is headquartered in Florianópolis, the capital of the state of Santa Catarina. A public institution, it offers free education and stands out as one of the best state universities in the country. Its mission is to commit knowledge management to the current situation and future of Santa Catarina.

Webometrics Ranking: The State University of Santa Catarina (Udesc) remains one of the best in Brazil, in 26th place – in total, 1,676 institutions in the country were analyzed.
The university occupies the 45th position in the Latin American ranking , with 3,797 institutions, and the 877th place in the world list, composed of 21,250 institutions from 226 countries.

There are 1,222 places available in 46 undergraduate courses. The opportunities are for 11 centers distributed in the cities of Balneário Camboriú, Chapecó, Florianópolis, Ibirama, Joinville, Lages, Laguna, Pinhalzinho and São Bento do Sul.

Udesc has an affirmative action program. 30% of places are reserved for each course, and distributed as follows:

20% for candidates who have completed their primary and secondary education in public educational institutions;

10% for black candidates, understood as people who have phenotypes that characterize them in society as belonging to the black racial group.

01-(UDESC-SC-019)

A simple way to measure an individual’s reaction time is to observe how long it takes for an individual to close his or her hand and hold a freely falling ruler. Figure 1 shows two images. One shows an open hand with a ruler above it as it is released. The other image shows the ruler being held, and the distance h traveled by the ruler in free fall is recorded .

Two participants performed this reaction test. Participant A recorded a height h and participant B recorded h/2 .

Select the alternative that corresponds to the ratio between the reaction times t _A /t _B .

02-(UDESC-SC-019)

Consider a spherical balloon of radius R filled with air, with half of its volume outside and the other half inside water. The balloon is tied by a string that is fully stretched, as shown in the figure.

Knowing that d _air and d _water correspond, respectively, to the density of air and water, select the alternative that corresponds to the modulus of tension in the rope .

A. . .g.(2d _water – d _air )

B. . .g.(2d _water – 2d _air )

C. . .g.(2d _water – d _air )

D. . .g.(d _air – d _water )

E. . .g.(d _water – 2d _air )

03-(UDESC-SC-019)

Consider two skaters skating together at the same speed v . Skater A has mass m and skater B has mass 2m .

At a given moment, skater A pushes B and, immediately, A’s speed goes to zero.

Disregard any friction forces , and select the alternative that corresponds to the percentage variation in skater B’s speed after the push.

A. ( ) 25% B. ( ) -50% C. ( ) -25% D. ( ) 50% E. ( ) -33%

04-(UDESC-SC-019)

Consider a container of volume v whose coefficient of volumetric expansion is _R . A liquid with coefficient of volumetric expansion _l is placed in the container until it is completely filled. After

a temperature variation t, the container and the liquid have their volumes expanded, and a volume of liquid overflows.

Select the alternative that corresponds to the value ( l – _R ). t.

A. ( ) 0.2 B. ( ) 10 C. ( ) 5 D. ( ) 0.1 E. ( ) 2

05-(UDESC-SC-019)

Consider that the average value of kWh is R$ 0.50. An electric shower has a power of 7000

W and a bulb has a power of 100 W.

Select the alternative that corresponds, respectively, to the energy consumption value, in 30 days, of a person who spends an average of 20 minutes taking a shower every day, and to the consumption value of a light bulb that is on all day.

A. ( ) R$35.00 and R$36.00

B. ( ) R$14.00 and R$14.40

C. ( ) R$35.00 and R$14.00

D. ( ) R$14.00 and R$36.00

E. ( ) R$35.00 and R$14.40

06-(UDESC-SC-019)

The figure shows a circuit placed above a magnet , whose magnetic field is restricted by the gray area, and the magnetic field lines are perpendicular to the plane of the circuit.

Analyze the propositions in relation to the figure .

I. When we move the circuit and the magnet together in opposite directions, along the y direction, current appears in the circuit.

II. When we move only the magnet, along the x direction, current is observed in the circuit.

III. If the magnetic field varies over time, current appears in the circuit.

IV. When the circuit and the magnet are moved together in the same direction and at the same speed, along the y direction, current is observed in the circuit.

V. When the circuit and the magnet move together in the same direction and at the same speed, along the x direction, current appears in the circuit.

Select the correct alternative .

A. ( ) Only statements I, II and IV are true.

B. ( ) Only statements I, III and V are true.

C. ( ) Only statements I, II and III are true.

D. ( ) Only statements II, IV and V are true.

E. ( ) Only statements III, IV and V are true.

07-(UDESC-SC-019)

A resistor with a resistance of 10 Ω is connected in parallel with a resistor with a resistance of 40 Ω. A voltage source of 12 V is applied to the combination.

Select the alternative that corresponds to the total electric current in the circuit and the power dissipated in the 40 Ω resistor, respectively.

A. ( ) 3.6A and 1.5W B. ( ) 0.24A and 2.3W C. ( ) 1.5A and 3.6W D. ( ) 0.3A and 3.6W E. ( ) 1, 5A and 2.3W

08-(UDESC-SC-019)

Two moles of ideal gas are compressed isothermally, at room temperature of 25ºC, until the volume of this gas is reduced by half.

Select the alternative that best represents the ratio between the initial and final pressures of the gas.

A. ( ) 2 B. ( ) 4 C. ( ) 1/4 D. ( ) 1 E. ( ) ½

09-(UDESC-SC-019)

The distance an object should be placed from a concave mirror with a radius of curvature of 50cm

so that the image of this object has the same orientation and measures 4/3 of the size of the object is:

A. ( ) 87.5 cm

B. ( ) 6.25 cm

C. ( ) 43.75 cm

D. ( ) 12.5cm

E. ( ) 116.66 cm

10-(UDESC-SC-019)

In 1900 Max Planck proposed the quantization of energy to explain blackbody radiation .

Planck’s postulate proposes that energy is given by E = nhf, where E is the energy, n is an integer, f is the frequency and h is a constant that later became known as Planck’s constant.

Select the alternative that corresponds to the unit of measurement in the international system of units .

A. ( ) Kg.m ² /s B. ( ) Kg.m/s C. ( ) Kg.m ² /s ² D. ( ) Kg.m/s E. ( ) Kg.m/s ²

11-(UDESC-SC-019)

A glass containing 200ml of water was placed in the refrigerator until the temperature reached minus 5ºC.

The glass was then removed from the refrigerator and placed on a table in a kitchen where the room temperature was 10ºC.

Select the alternative that corresponds to the total heat received by the water until it reaches thermal equilibrium.

A. ( ) 1.5kcal B. ( ) 16.5kcal C. ( ) 18.5kcal D. ( ) 19.5kcal E. ( ) 4.1kcal

12-(UDESC-SC-019)

A tank 50 cm deep contains water with a density of 1000 kg/m3 ^. A small sphere of radius 2.0 cm, made of material with a density of 920 kg/m3 ^, is placed at the bottom of the tank and released from rest.

Disregard the resistance of the water to the movement of the sphere.

Select the alternative that corresponds to the value of the rise time.

Commented resolution of Physics questions from the State University of Santa Catarina (UDESC – 2019)

01-

Body abandoned at a certain height h above the ground

R-B

02-

Theoretical summary

Placing the forces acting on the balloon:

R- And

03-

Amount of movement of the system before the push:

Q _sa = m _A .V _A + m _B .V _B = mv + 2mv Q _sa = 3mv

Amount of movement of the system after the push:

Q _sd = m _A .V _A + m _B .V _B = m.0 + 2mV _B Q _sd = 2mV _B

By the principle of conservation of momentum Q _sa = Q _sd 3mv = 2mV _B

V _B = 1.5v.

B’s speed varied from v to 1.5v, that is, by 50% .

R-D

04-

Dilation of liquids

R-D

05-

Shower t = 30 daysx20/60h = 10 h P = 7000 W = 7 kW energy W = P. t = 7.10

W = 70 kWh price C$ = 70×0.5 C$ = 35.00

Lamp t = 24×30 = 720 h P = 100 W = 0.1 kW energy W = P. t = 0.1.720

W = 72 kWh price C$ = 72×0.5 C$ = 36.00

A- A

06-

Electromotive force induced by motion

Electromotive force generated by a moving conductor in a uniform electric field

Electromotive force ε generated by a moving conductor immersed in a uniform electric field; this conductor behaves like a mechanical electricity generator with emf ε.

The direction of the induced electric current is given by Lenz’s law “the induced electromotive force and the induced current generate a magnetic flux that opposes the variation of the flux causing the induction” .

I. True – When we move the circuit and the magnet together in opposite directions, along the y direction, current appears in the circuit because there is a variation (in this case a decrease) in the area of the loop.

II. True – the area of the coil is also varying.

III. True – see theory above.

IV. False – there is no variation in the area.

V. Fasa – see IV.

R-C

07-

In parallel association, the resistance of the equivalent resistor can be calculated by R _eq = product/sum = (40 x 10)/(40 + 10) = 400/50 R _eq = 8 Ω.