Physics

Forces, Energy and Machines

267 Questions

Forces, energy, and machines are fundamental physics concepts focusing on mechanics, work, power, and simple machines. These topics regularly appear in general science sections of competitive exams. Use these questions to practice calculating resultant forces, mechanical advantage, and work done in various scenarios.

Resultant force calculationsMechanical advantage of leversWork and power equationsApparent weight in elevatorsBending moments

Forces, Energy and Machines Questions

Multiple choice general knowledge math & puzzles

A monkey is climbing a 10 meters long bamboo. It climbs 2 meters a second and slips 1 meter in the next second. How long will it take to climb the bamboo?

  1. 18 seconds

  2. 20 seconds

  3. 19 seconds

  4. 21 seconds
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The monkey gains 1 meter every 2 seconds (2m up, 1m down). After 16 seconds, it is at 8 meters. In the next second (the 17th), it climbs 2 meters to reach 10 meters and finishes. However, the standard calculation for these riddles often results in 19 if the slip is counted differently, but 17 is the logical physical answer.

Multiple choice general knowledge science & technology

The amount of work done by a carpenter holding a 20kg sheet of drywall at 2.5 meters for 30 minutes is...

  1. 0 J

  2. 500 J

  3. 50 J

  4. 100 J
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Work is defined as force multiplied by displacement in the direction of the force. Since the carpenter holds the drywall stationary, there is no displacement, so the work done is zero joules. The time spent holding and the weight of the object don't matter when nothing moves.

Multiple choice general knowledge

An ant can lift ----------- times of it’s own weight.

  1. Twenty

  2. Fourty

  3. Fifty

  4. Sixty
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ants are incredibly strong relative to their size. They can lift and carry objects 10-50 times their own body weight, with 50 times being at the upper end of their capability. This strength comes from their specialized muscle structure and small size, which gives them a high strength-to-weight ratio.

Multiple choice general knowledge math & puzzles

The foreman needs to move the ladder. The ladder falls upon the foreman. If you add the two positions in the prior sentences (e.g.,"falls" would equal 10) at which the former use of ladder and the latter use of foreman fall, then count upwards to the first prime number you have:

  1. 31

  2. 29

  3. 13

  4. 23
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The first 'ladder' is the 7th word. The second 'foreman' is the 13th word. 7 + 13 = 20. Counting upwards from 20, the first prime number encountered is 23. Options like 29 or 31 are primes but not the 'first' one after 20.

Multiple choice general knowledge math & puzzles

Tony and Tommy have been experimenting with balloons. They found that if they fill 5 balloons with helium, they can use the balloons to lift 50 pounds. Three of the same balloons filled with hydrogen lift 60 pounds. Ten filled with neon lift 20 pounds. How many pounds could the men lift with 5 neon, one hydrogen, and two helium balloons?

  1. 30 Pounds

  2. 40 Pounds

  3. 50 pounds

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

1 Helium balloon lifts 10 lbs (50/5). 1 Hydrogen lifts 20 lbs (60/3). 1 Neon lifts 2 lbs (20/10). Total lift = (5 * 2) + (1 * 20) + (2 * 10) = 10 + 20 + 20 = 50 pounds.

Multiple choice general knowledge

It is easier to roll a stone up a sloping road than to lift it vertical upwards because

  1. work done in rolling is more than in lifting

  2. work done in lifting the stone is much more than rolling it

  3. work done in both is same but the rate of doing work is less in rolling

  4. work done in rolling a stone is less than in lifting it
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Rolling a stone up a slope requires less work than lifting it vertically because the force needed is much smaller when spread over a longer distance (mechanical advantage). When lifting vertically, you must overcome the full weight directly. Rolling spreads the work over more distance with less force. The other options incorrectly claim rolling requires more work or the same work.

Multiple choice general knowledge science & technology

It is easier to roll a stone up a sloping road than to lift it vertical upwards because

  1. work done in rolling is more than in lifting

  2. work done in lifting the stone is much more than rolling it

  3. work done in both is same but the rate of doing work is less in rolling

  4. work done in rolling a stone is less than in lifting it
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Work = force × distance. When rolling up a slope, the effective force needed is reduced (mg sinθ vs mg for vertical lift), so less work is done over the longer distance along the slope compared to lifting vertically.

Multiple choice

A man climbs up and a monkey climbs down a rope hanging from a tree with same uniform acceleration separately. If the respective masses of monkey and man are in the ratio 3 : 2, the common acceleration must be

  1. 7/g

  2. 5g

  3. g/9

  4. g/5

  5. g/11
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let T be the tension of a rope. When man climbs up with acceleration a, ... T - m1g = m1a …(1) When a monkey climbs down with same acceleration a ... m2g - T = m2a ….(2) Adding (i) and (ii), we get (m2 - m1)g = (m1 + m2)a Or (1 - m1 / m2)g = (m1 / m2 + 1)a Or (1 - 2 / 3)g = (2 / 3 + 1)a Or (1 / 3)g = (5 / 3)a Or, a = g / 5. Clearly, it is not equal to 5g, hence it is a wrong option.