HSSC-I (Class-11) Solved Physics MCQs; Unit-3: Forces and Motions; (New Book/KPK Text Board, Peshawar) With Verified Answers 


1. A ball is thrown vertically upwards at 19.6 m/s. For its complete trip (up and back down to the starting position), its average speed is:




... Answer is B. 9.8 m/s.
Average velocity = total displacement / total time --- by using Vf = Vi + at to calculate t. (vi = 19.6 m/s (given), vf = 0 m/s (at highest point), and g = - 9.81 m/s² (-ve due to upward motion), we get t = 2 s, so total time of flight will = 2 s (upwards) + 2 s (downwards) = 4 s ---- Now using s = vi t + (1/2) at² we will get the upwards motion distance s = 19.6 m, thus the total distance of the trip is =19.6 m (upwards) + 19.6 m (downwards) = 39.2 m, so Average velocity = 39.2 / 4 = 9.8 m/s. Thus Correct answer is option B.


2. If you throw a ball downward, then its acceleration immediately after leaving your hand, assuming no air resistance, is




... Answer is A. 9.8 m/s²
While throwing the ball down its velocity depends on the force with which it is thrown ( ie. by applying a greater force greater will be the velocity) but its acceleration is the same as in the free fall motion which is 9.8 m/s².


3. The time rate of change of momentum gives




... Answer is A. Force
F = Δp/Δt


4. The area between the velocity-time graph is numerically equal to:




... Answer is B. Displacement
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5. If the slope of the velocity-time graph gradually decreases, then the body is said to be moving with:




... Answer is B. Negative acceleration
Negative Acceleration is also called Deceleration or Retardation


6. A 7.0 kg bowling ball experiences a net force of 5.0 N. What will be its acceleration?




... Answer is D. 0.71 m/s²
 F = ma or a= F/m = 5 N/7 kg=  0.71 m/s²

7. SI unit of impulse is: :




... Answer is B. N s
J = F x Δt


8. A ball with original momentum +4.0 kg m/s hits a wall and bounces straight back without losing any kinetic energy. The change in momentum of the ball is:




... Answer is A. + 4 N s
Initial momentum = Final Momentum = + 4 N s

9. A body is traveling with a constant acceleration of 10 m s⁻². If S₁ is the distance traveled in 1st second and S₂ is the distance traveled in 2nd second, which of the following shows a correct relation between S₁ and S₂?




... Answer is C. S₂ = 3S₁
Assuming the body is starting from rest vi = 0 m/s and a=10m/s^2, using 2nd equation of motion S = vit + (1/2) at² ---- For t = 1 s S₁ = 0 + (1/2)10 t^2=5(1)^2 = 5 m for t = 2 s, S₂ = 0 + (1/2)10(2)^2 = 20 m So, S₂ = 20 - S₁ = 20 m - 5 m = 15 m = 3 x 5 m = 3 S₁


10. During projectile motion, the horizontal component of velocity:




... Answer is C. Remains constant
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11. A projectile is thrown horizontally from a 490m high cliff with a velocity of 100 m s⁻¹. The time taken by the projectile to reach the ground is




... Answer is D.  10 s 
 T = v₀ sinθ / g = 100 m s⁻¹ sin (90°)/10 m s⁻² = 10 s


12. A projectile is launched at 45° to the horizontal with an initial kinetic energy of E. Assuming air resistance to be negligible what will be the kinetic energy of the projectile when it reaches its highest point?




... Answer is A.  0.50 E
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13. To improve the jumping record the long jumper should jump at an angle of




... Answer is B. 45°
The maximum range of the projectile is 45°


14. Range of a projectile on a horizontal plane is the same for the following pair of angles:




... Answer is B. 43° and 47°
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