# Common Physics Practice Test 1

Question – 1

1. Which of following is required to keep a body in static equilibrium?

• A. Unbalanced force

• B. Acceleration

• C. Non-zero resultant force

• D. Non-zero tension

• Answer Explanation:To keep body in static equilibrium we require either balanced force or body should be moving with uniform velocity (not accelerating). For example, a body kept on horizontal plane is in static equilibrium because weight (acting downwards) being balanced by the normal force acting upwards. Hence, B is correct answer option. If an unbalanced force acts on a body it starts accelerating and hence A is incorrect. For a body to be in equilibrium, it should have zero acceleration hence C is incorrect. For non-zero resultant force, unbalanced force results and hence D is incorrect as well. Tension is nothing but force, hence non-zero tension results in unbalanced force which does not result in equilibrium state therefore, E is incorrect as well.

Question – 2

2. If an electron jumps from higher energy shell of energy E2 to lower energy shell E1, what will be the wavelength of the photon emitted during the process?

• A.

• B.

• C.

• D.

• E.

• Answer Explanation:Energy of photon is given as E= h??
Speed of a electromagnetic wave is given as c= ????
Therefore, Or
(since E=E2-E1)
Hence, E is the correct answer option.

Question – 3

3. If a liquid of density of 810 Kg/m3 and mass 0.950 Kg is kept in a vessel of negligible mass, what would be its volume in cm3?

• A. 1.17 X 10-3

• B. 11.7

• C. 117

• D. 1.17

• E. 1170

volume = 0.950/ 810
volume = 1.17 X 10-3 m3
lm3 = 106 cm3
Hence, converting volume in m3 to cm3 we get
volume = 1.17 X 10-3 106 cm3 or volume = 1170 cm3
Hence, E is the correct answer option.

Question – 4

i. Body in equilibrium, has uniform velocity.
ii. Body in equilibrium, has non-zero acceleration.

• A. Both the statements are true

• B. Both the statements are false

• C. Statement i is true but ii is false

• D. Statement ii is true but i is false

• E. Statement ii is correct explanation for the statement i

• Answer Explanation:For a body in equilibrium, there may be two cases associated with it.1) In equilibrium all the forces cancel out each other and hence body stays at rest forever unless and until some unbalanced force acts on it.
2) A body may be in equilibrium if it is moving with uniform velocity. Since, acceleration is the time rate of change of velocity, constant velocity results in zero acceleration.

Therefore, statement i is correct but ii is incorrect hence C is correct answer option.

Question – 5

5. 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 Explanation:Weight of the block of ice is given as W= mg
400 = m X 9.8
Or m= 40.82 kg
Hence, C is the correct answer option.

Question – 6

6. In which of the following does the body experience a constant acceleration?

• A. A body falling freely under gravity (Atmospheric resistance neglected)

• B. A body sliding down an inclined plane

• C. A spherical ball rolling on the floor

• D. Man walking through the lane

• E. There is nothing like constant acceleration

• Answer Explanation:A freely falling object under gravity experiences a constant acceleration of 9.8 m/s2 if air resistance is neglected. For all other motions acceleration cannot remain constant as opposing force friction develops which resists body’s motion. Therefore, A is the correct answer as it is the only option that can bring out this concept distinctly.

Question – 7

7. Which of the following is conserved in inelastic collision?

• A. Momentum

• B. Kinetic energy

• C. Force

• D. Mechanical energy

• E. Velocity

• Answer Explanation:Inelastic collision is a collision in which total momentum of the body remains conserved while kinetic energy or mechanical energy is not conserved due to heat or sound loss. Hence, A is the correct answer option; B and D are incorrect options. According to Newton’s second law, time rate of change of momentum is force applied i.e.F= dp/dt.Since in inelastic collision momentum remains conserved dp=0,force applied also becomes zero. Therefore, C is incorrect. Since there is loss of some kinetic energy; velocities of the bodies after the collision cannot remain same. Hence, E is incorrect as well.

Question – 8

8. A box of mass 1.2 Kg is connected at the bottom of a spring that has spring constant of 20 N/m. If the whole system is set into simple harmonic motion, what will be the frequency of oscillation? (Assume mass of the spring is negligible)

• A. 1 Hz

• B. 0.64 Hz

• C. 1.06 Hz

• D. 0.06 Hz

• E. 16.67 Hz

• Answer Explanation:Time period of oscillation is given as T= 2?????(m/k)
T= 2?????(1.2/20) Or T= 2?? X 0.25
T=1.57 s
Frequency is reciprocal of time period. Hence,
??=0.636 Hz
Since, only B is the closest to the correct answer hence it is the correct answer option.

Question – 9

9. A wave is represented as . What is the amplitude and direction of wave propagation?

• A. 2.5 m and negative of z

• B. 2.5 cm and positive of z

• C. 2.5 cm and negative of z

• D. 2.5 m and positive of z

• E. Wave is not travelling at all

• Answer Explanation:A general sine wave is represented as y= A sin (??t ?? z )
If a wave travels along negative of z direction, then its displacement is always negative. For example, let initial position of a wave be 0 and the wave travels along negative of z direction to a position -5 cm. Hence, the displacement of wave from the initial point is -5 cm. But for a wave travelling along positive of z-direction displacement is always positive. Due to this, +z signifies the wave is travelling in negative of z direction and -z signifies the wave is travelling in positive of z direction. Hence, comparing the wave equation given in the question and 1 we get A = 2.5 cm and the wave is travelling in negative of z direction hence C is the correct answer option.

Question – 10

10. A missile is fired at an angle of 300 from the horizontal. If the highest point the missile can reach is 200 m, what was the velocity with which the missile was fired?

• A. 125.22 m/s

• B. 120.34 m/s

• C. 100.12 m/s

• D. 121.22 m/s

• E. 150.4 m/s

• Answer Explanation:The maximum height that a projectile can attain is given as h= v2 sin2 ?? / 2g
200= v2 (sin 300)2 / 2 X 9.8
200 X 2 X 9.8 = v2 (sin 300)2
v= 125.22 m/s
Hence, A is the correct answer option.

Question – 11

11. At which angle does a ray of light reflect back to the same medium after being incident on another medium of a different refractive index?

• A. Less than critical angle

• B. Greater than critical angle

• C. 00

• D. 900

• E. Light will not reflect at any angle

• Answer Explanation:Critical angle is the angle above which total internal reflection will occur. That is, if a ray of light is incident on an interface separating two different mediums, making an angle greater than the critical angle, then the ray of light will reflect back. This will only take place at an angle greater than the critical angle. Hence, A is an incorrect answer option whereas B is the correct answer option. At 00 a ray of light is incident on a medium orthogonally. If both the mediums are of same refractive indices then only will the ray of light reflect back. Otherwise we will have refraction of light. Hence C is an incorrect option. At 00 a ray of light will travel along the interface separating the mediums. There will be no reflection or refraction. Hence, D is an incorrect answer option. Light will reflect at an angle greater than the critical angle. Hence, E is an incorrect answer option.

Question – 12

12. If the external force applied on a body is zero, which of the following is true regarding angular momentum?

• A. It becomes zero

• B. It becomes negative

• C. It remains constant

• D. It decreases

• E. It increases

• Answer Explanation:Angular momentum is conserved if net torque is zero and this is known as law of conservation of angular momentum.Lsystem = constant|torque = 0
Torque is given as
Torque = r X F
Since force applied here is zero, torque measured will be zero as well. Therefore, equation 1 is valid here and angular momentum remains constant. Hence, C is the correct answer option.

Question – 13

13. Which of the following will have the maximum buoyant force?

• A. 100 g of wooden plank floating on water

• B. 200 g of wooden plank floating on water

• C. 50 g of wooden plank floating on water

• D. 250 g of wooden plank floating on water

• E. 400 g of wooden plank floating on water

• Answer Explanation:Buoyant force is equal to the weight of the fluid displaced by the object. Since, among all the wooden planks 400 g is of maximum weight, hence water displaced by it will be maximum, and therefore, buoyant force will be maximum as well. Hence, E is the correct answer option.

Question – 14

14. Which of the following is a correct statement?

• A. Flux lines for a positive charge radiate outwards

• B. Flux lines for a negative charge radiate outwards

• C. Two like charges attract each other

• D. Two unlike charges repel each other

• E. Charge on a neutron is +e

• Answer Explanation:Electric flux lines originate from a positive charge and terminate at a negative charge. Hence, flux lines for a positive charge always radiate outwards. Therefore A is the correct answer option. Flux lines for a negative charge are directed inwards. Hence, B is an incorrect answer option. Two like charges either positive or negative always repel each other. Hence, C is an incorrect answer option. Unlike charge like a negative charge kept closer to a positive charge will develop force of attraction not repulsion. Therefore, unlike charges always develop force of attraction not repulsion between them. Hence D is incorrect. Neutron has no charge in it. Hence E is incorrect as well.

Question – 15

15. When the temperature of a body increases, its _________.

• A. internal energy decreases

• B. internal energy becomes zero

• C. internal energy increases

• D. internal energy remains constant

• E. entropy decreases