ACT Physics Practice Test 4

Question – 1

1. What would be the work done by a force to stop a car of mass 500 kg moving with a velocity of 24 m/s?

  • A. 144000 J

  • B. 100000 J

  • C. 12000 J

  • D. 6000 J

  • E. 169000 J

  • Answer:A

  • Answer Explanation:W = KE2 – KE1 Or W = 1/2 m(v2 – u2)W = 1/2 X 500 X (02 – 242)Or W = -144000 JNegative sign is because work is done in stopping the car (retardation). Same would be coming in positive if the work is done in moving the car. Hence, A is the correct answer option.


Question – 2

2. A car starts from a point A at 9 AM and reaches point B at 11 AM. If A and B are separated by 100 km and the car is moving with uniform speed, what is the speed of the car for the entire travel in m/s?

  • A. 15.7 m/s

  • B. 13.9 m/s

  • C. 11.3 m/s

  • D. 10.4 m/s

  • E. 14.5 m/s

  • Answer:B

  • Answer Explanation:Speed is given as v = d/tv = 100/2 or v = 50 km/hConvert hours into seconds and km into m.50 km/h = 50 X 1000/3600 m/sor 50 km/h = 13.9 m/sHence, B is the correct answer option.


Question – 3

3. A rotor with uniform angular speed of 210 s-1 needs a torque of 250 Nm from an engine. What would be the power of the engine required for the torque?

  • A. 54500 W

  • B. 52500 W

  • C. 34600 W

  • D. 1.19 W

  • E. None of the above choices

  • Answer:B

  • Answer Explanation:Power associated with torque is given as P = ?? ??P = 250 X 210Or P = 52500 WHence, B is the correct answer option.


Question – 4

4. What would be the number of electric lines of forces coming out of a unit charge?

  • A. 5.5 X 107

  • B. 8.5 X 10-7

  • C. 2.15 X 107

  • D. 1.11 X 10-5

  • E. 1.81 X 10-8

  • Answer:E

  • Answer Explanation:Electric lines of forces are nothing but electric flux lines. Electric flux originating from a charge is given as?? = Q/??0——-(1)?? = -(1.6 X 10-19) / (8.85 X 10-12) Or ?? = – 1.81 X 10-8Negative sign signifies that the electric field lines for an electron are inwards rather than outwards. Neglecting the negative sign, number of electric lines of force becomes 1.81 X 10-8. The result suggests that, electric flux for an electron is of a very minute quantity.Hence, E is the correct answer option.


Question – 5

5. A tuning fork vibrates with a frequency of 500 Hz. If the speed of sound in air is 343 m/s, what is the distance the sound travels when the tuning fork makes 100 oscillations?

  • A. 34.3 m

  • B. 50.4 m

  • C. 5 m

  • D. 76.8 m

  • E. 68.6 m

  • Answer:E

  • Answer Explanation:v = ????343 = 500 X ?? Or ?? = 0.686 mThis is the distance which the sound travels in one oscillation. The distance traveled in 100 oscillations is d = 100 X 0.686 m Or d = 68.6 mHence, E is the correct answer option.


Question – 6

6. A force acting on a body of mass 10 kg changes its velocity from 3 m/s to 6.7 m/s in 20 seconds. What is the magnitude of the force applied on the body?

  • A. 10 N

  • B. 3.77 N

  • C. 1.85 N

  • D. 4.55 N

  • E. 2.33 N

  • Answer:C

  • Answer Explanation:F = m(v-u)/tF= 10 X (6.7-3)/20Or F = 1.85 NHence, C is the correct answer option.


Question – 7

7. Which of the following is a unit of power?

  • A. J

  • B. Nm/s

  • C. W/s

  • D. W/s

  • E. None of the above choices

  • Answer:B

  • Answer Explanation:P = W/t and W = F.dSI unit of force (F) is N, displacement (d) is m and time (t) is s.Therefore P = Nm/s Or, P = Nm/sHence, B is the correct answer option.


Question – 8

Which of the following statement(s) is true in accordance to the given figure?

  • A. 2

  • B. 1

  • C. 3

  • D. Both 1 and 2

  • E. Both 2 and 3

  • Answer:A

  • Answer Explanation:Force experienced by the beta particle is given as F = qvB sin ??F = 1.6 X 10-19 X 104 X 0.01 X sin 90oF = 1.6 X 10-17 X 1 NF = 1.6 X 10-17 NHence, B is the correct answer option.


Question – 9

9. What is the buoyant force exerted on a 20 cm3 block of iron submerged completely inside water?

  • A. 0.234 N

  • B. 0.111 N

  • C. 2.289 N

  • D. 1.34 N

  • E. 0.196 N

  • Answer:E

  • Answer Explanation:Buoyant force is given as FB = ??gVAs the block is submerged completely, volume of water displaced is equal to the volume of the block = 20 cm3.As the volume is given in cm3 we need to convert it into m3.FB = 1000 X 9.8 X 2 X 10-5Or FB = 0.196 NHence, E is the correct answer option.


Question – 10

10. A particle in SHM has a time period of 3 s and amplitude of 0.1 m. What is the displacement of the particle after 1 s?

  • A. 0.011 m

  • B. 0.23 m

  • C. 0.087 m

  • D. 0.754 m

  • E. Zero

  • Answer:C

  • Answer Explanation:y(t) = Asin(2??/T)ty(1) = 0.1 X sin(2??/3)1y(1) = 0.1 X ???3/2 Or y(1) = 0.087 mHence, C is the correct answer option.


Question – 11

11. Which of the following consist of the highest energy photons?

  • A. X-ray

  • B. Visible light

  • C. Infrared

  • D. Radio waves

  • E. Microwaves

  • Answer:A

  • Answer Explanation:All of the options given above are electromagnetic waves. They travel at 3 X 108 m/s. Radio waves have energy in order of 10-9 eV (electron-volt) to 10-6 eV. Microwaves have energy in order of 10-5 eV to 10-2 eV. Infrared have energy in order of 1 to 10-2 eV. Visible light have energy in order of 1.6 eV to 3.2 eV. X-rays have energy in order of 102 to 105 eV. Hence on comparing energies of all the electromagnetic waves given above, X-ray has the highest energy. Hence, A is the correct answer option.


Question – 12

12. Consider the figure given below for a system of two iron blocks connected with a common pulley. If the block A weighs 200 N, what would be the mass of the iron block B to keep the whole system in static equilibrium?

  • A. 20.41 kg

  • B. 15.57 kg

  • C. 22.23 kg

  • D. 34.45 kg

  • E. 21.45 kg

  • Answer:A

  • Answer Explanation:As the whole system is in static equilibrium, there will be no motion in the blocks. In other words, weight of both the iron blocks should be the same.W = mg200 = m X 9.8Or m = 20.41 kgTherefore, A is the correct answer option.


Question – 13

13. Air is filled in a piston of capacity 100 liters at 313 K. At what temperature should the piston be heated so that volume increases to 120 liters for an isobaric process?

  • A. 375.6 K

  • B. 373 K

  • C. 300.45 K

  • D. 413.5 K

  • E. 343.7 K

  • Answer:A

  • Answer Explanation:Isobaric process is carried out at a constant pressure. Since, pressure is constant here, we have to apply Charles’s law. According to Charles’ lawV1 / T1 = V2 / T2100/313 = 120/T2 Or T2 = 375.6 KHence, A is the correct answer option.


Question – 14

14. A spring balance measures the weight of a block of ice as 400 N. What is the mass of the block of ice?

  • A. 34.65 kg

  • B. 45.66 kg

  • C. 40.82 kg

  • D. 24.87 kg

  • E. 76.56 kg

  • Answer:C

  • Answer Explanation:W = mg400 = m X 9.8Or m = 40.82 kgHence, C is the correct answer option.


Question – 15

15. What would be the power of a convex lens of focal length 10 cm?

  • A. -0.2 dioptre

  • B. -0.1 dioptre

  • C. 10 dioptre

  • D. -10 dioptre

  • E. 0.05 dioptre

  • Answer:C

  • Answer Explanation:Power of a lens is given as P = 1/??Power of converging or convex lens is positive. Therefore P = 1/10 cmSI unit of power is m-1. Hence we need to convert the unit from cm-1 to m-1.P = 1/0.1 Or P = 10 m-1There is another SI unit for power which is equivalent to m-1and is known as dioptre.Therefore P = 10 dioptre. Hence, C is the correct answer option.


Score: 0/10

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