Simple Machines and Work Quiz

Grade 7 · Science · Quiz

Test your knowledge of the six simple machines, mechanical advantage, and calculating scientific work.

Questions

1. A force of 20 newtons is applied to move a box 5 meters. How much work is done?

   1. 4 J
   2. 25 J
   3. 100 J
   4. 15 J
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   Answer: 100 J

   W = F × d = 20 N × 5 m = 100 joules. Work requires both force and displacement in the direction of the force.

2. Which type of lever has the fulcrum between the effort force and the load?

   1. First-class lever
   2. Second-class lever
   3. Third-class lever
   4. Fixed lever
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   Answer: First-class lever

   A first-class lever has the fulcrum (pivot) in the middle, between the effort force and the load. A seesaw and scissors pivot are classic examples.

3. What is the mechanical advantage of a machine that requires 10 N of input force to produce 40 N of output force?

   1. 0.25
   2. 4
   3. 30
   4. 50
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   Answer: 4

   Mechanical advantage = output force / input force = 40 N / 10 N = 4. This machine multiplies your force by four, though you must apply the force over a greater distance.

4. A single fixed pulley changes both the direction and the magnitude of the applied force.

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   Answer: False

   A single FIXED pulley only changes the direction of the force (you pull down instead of lifting up). It does not provide any mechanical advantage — the output force equals the input force.

5. Which simple machine is most similar in function to a screw?

   1. Pulley
   2. Lever
   3. Inclined plane
   4. Wheel and axle
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   Answer: Inclined plane

   A screw is an inclined plane wrapped in a spiral. They both convert a smaller force applied over a longer distance into a larger force over a shorter distance.

6. A pair of scissors is an example of which combination of simple machines?

   1. Two pulleys and two wedges
   2. Two levers and two wedges
   3. Two inclined planes and a wheel
   4. Three levers
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   Answer: Two levers and two wedges

   Scissors consist of two levers (the handles and blades pivoting at a fulcrum — the screw in the center) plus two wedges (the sharpened blades that cut through material).

7. Work is calculated using the formula W = F × ______ (the distance an object moves).

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   Answer: d

   The formula W = F × d stands for Work = Force × distance. The 'd' represents the displacement of the object in the direction of the applied force, measured in meters.

8. Which statement about simple machines is TRUE?

   1. They reduce the total amount of work needed
   2. They always increase the distance over which force is applied
   3. They can change the size or direction of a force
   4. They create energy from nothing
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   Answer: They can change the size or direction of a force

   Simple machines change the size (magnitude) or direction of a force — never the total energy required. They cannot reduce total work or create energy; they simply make tasks more manageable.

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