Home › Board exam reviewer › Physics: mechanics

Physics: mechanics: board exam questions with solutions

On the ECE exam under General Engineering and Applied Sciences (GEAS) and the REE exam under Engineering Sciences and Allied Subjects (ESAS). Try each question before you open its solution, then practise with fresh numbers below: 3 computed question types on this topic.

Loading the reviewer… (it needs JavaScript)

Questions

1. A stone is dropped from rest at 45 m above the ground. Neglecting air resistance, how long does it take to land? (g = 9.81 m/s²)

  1. 4.59 s
  2. 3.03 s
  3. 9.17 s
  4. 2.14 s
Show the answer and solution

Answer: B. 3.03 s

h = ½gt², so t = √(2h/g) = √(90/9.81) = 3.03 s.

2. A ball is launched at 30 m/s and 30° above the horizontal on level ground. Find its horizontal range. (g = 9.81 m/s²)

  1. 45.87 m
  2. 79.45 m
  3. 91.74 m
  4. 68.81 m
Show the answer and solution

Answer: B. 79.45 m

R = v²sin 2θ/g = 900 × sin 60°/9.81 = 900 × 0.866/9.81 = 79.45 m.

3. What average net force accelerates a 1200 kg jeepney from rest to 20 m/s in 8 s?

  1. 3000 N
  2. 2400 N
  3. 9600 N
  4. 1500 N
Show the answer and solution

Answer: A. 3000 N

a = 20/8 = 2.5 m/s², so F = ma = 1200 × 2.5 = 3000 N.

4. A 10 kg block slides down a 30° incline with coefficient of kinetic friction 0.2. Find its acceleration. (g = 9.81 m/s²)

  1. 4.91 m/s²
  2. 6.60 m/s²
  3. 1.70 m/s²
  4. 3.21 m/s²
Show the answer and solution

Answer: D. 3.21 m/s²

a = g(sin θ − μcos θ) = 9.81(0.5 − 0.2 × 0.866) = 9.81 × 0.3268 = 3.21 m/s². Ignoring friction gives 4.91 m/s².

5. One watt is equal to:

  1. 1 N·m
  2. 1 J·s
  3. 1 J/s
  4. 1 kg·m/s
Show the answer and solution

Answer: C. 1 J/s

Power is the rate of doing work, so 1 W = 1 J/s. N·m is a unit of energy or torque, and kg·m/s is a unit of momentum.

6. A 2 kg cart moving at 6 m/s collides with a stationary 4 kg cart and they stick together. What is their common velocity?

  1. 3 m/s
  2. 6 m/s
  3. 2 m/s
  4. 1.5 m/s
Show the answer and solution

Answer: C. 2 m/s

Momentum is conserved: 2 × 6 = (2 + 4)v, so v = 12/6 = 2 m/s.

7. A motor with 80% efficiency hoists a 500 kg load 20 m in 25 s at constant speed. What electrical input power does it draw? (g = 9.81 m/s²)

  1. 4.91 kW
  2. 3.92 kW
  3. 3.14 kW
  4. 98.1 kW
Show the answer and solution

Answer: A. 4.91 kW

P_out = mgh/t = 500 × 9.81 × 20/25 = 3924 W. P_in = 3924/0.80 = 4905 W ≈ 4.91 kW.

8. A 1000 kg car rounds a flat curve of radius 50 m at 20 m/s. What centripetal force is required?

  1. 400 N
  2. 20 000 N
  3. 4000 N
  4. 8000 N
Show the answer and solution

Answer: D. 8000 N

F = mv²/r = 1000 × 400/50 = 8000 N.

Worked examples with computed numbers

These numbers are fixed on this page; in practice they change every time.

9. A stone is dropped from rest from a height of 35 m. Ignoring air resistance, how long does it take to reach the ground?

  1. 3.57 s
  2. 1.89 s
  3. 7.14 s
  4. 2.67 s
Show the answer and solution

Answer: D. 2.67 s

h = ½gt², so t = √(2h/g) = √(2 × 35/9.81) = 2.67 s.

10. A ball is launched at 20 m/s, 20° above level ground. How far away does it land?

  1. 13.9 m
  2. 26.2 m
  3. 13.1 m
  4. 40.8 m
Show the answer and solution

Answer: B. 26.2 m

R = v²·sin 2θ/g = 20² × sin 40°/9.81 = 26.2 m.

11. What is the kinetic energy of a 124 kg mass moving at 2 m/s?

  1. 248 J
  2. 124 J
  3. 496 J
  4. 372 J
Show the answer and solution

Answer: A. 248 J

KE = ½mv² = ½ × 124 × 2² = 248 J.

Other topics in the same subjects

Physics: waves, electricity and magnetism · General chemistry · Thermodynamics · Engineering materials · Engineering economics · Engineering management · Computer fundamentals and programming · RA 9292 and ethics (electronics) · Fluid mechanics · Strength of materials · RA 7920 and ethics (electrical) · PEC Part 1: general requirements

An independent, free reviewer: not affiliated with the PRC or the Boards. Subject weights and passing rules are from the PRC examination programs and the laws (RA 9292, RA 7920); check the current PRC program before you file. Code questions follow the Philippine Electrical Code 2017 Part 1; check them against your own copy of the Code.