Mechanical Comprehension Practice Question Answers
1. The best answer is "c" because the question is geared toward the concept of inertia. A heavy, dense object possesses more inertia and requires a greater amount of force to accelerate it than an object that is less dense. Think of the difference between a basketball and a bowling ball. The bowling ball has more mass and requires greater force to move it along.
2. The correct answer is "a." Newton is known for his Laws of Motion. His first Law of Motion states that an object at rest tends to stay at rest just as an object in motion tends to stay in motion unless acted upon by an unbalanced force. A resting object, therefore, would have to be pushed or accelerated by an external force. Similarly, a moving object tends to keep moving in the same direction unless an opposing force comes to act upon it. Think of a front-end collision as an "unbalanced force" acting upon a moving object.
3. Shifting to a smaller gear will result in a slower speed of travel. Option "b" is the correct answer. The smaller gear will turn a complete revolution more often than will a larger gear. Therefore, a small gear requires many more revolutions to cover a specific distance than does a large gear. A larger rear controlling gear, though harder to "push," would cause the bicycle to pick up speed.
4. It is true that work is measured in joules but this answer is misleading. Work is defined as force x distance so 100 joules of work would be wrong. The correct answer is "c" because the distance moved and the force applied are the same regardless of whether a ramp and hand truck are used. The vertical distance of 4 feet is the same. The amount of force needed to move the 40 pound boxes is the same whether the force is applied straight up and down or on a ramp. The ramp may make the task easier for the worker to accomplish, but it does not change the amount of work to be accomplished.
5. The best answer is "d." While sliding the box along the floor may be easier and less dangerous than lifting it, no mechanical advantage is used. All the other answers use a mechanical advantage. A pry bar is a type of lever that provides a mechanical advantage. A screwdriver uses a mechanical advantage because the handle has a greater diameter than the point of the screwdriver. That is much like a big wheel (handle) geared to a smaller wheel (tip of screwdriver). A wheelbarrow provides more than one mechanical advantage. It uses leverage with a fulcrum; it also uses a wheel and axle arrangement.
6. The correct answer is "b." Kilograms are a unit measuring weight, akin to "pounds" in the American system of measuring weight. Joules is a measurement of work and kinetic energy. Liters are a measure of liquid volume. Substances such as gasoline or milk are often measured in liters.
7. The correct answer is "d." The other examples use the mechanical advantage of a wedge. A chisel splits wood by exerting a force on the wood in two directions. The "sand wedge" golf club applies a force against the ground and another in the direction of the golf ball. Wood axes are wedge shaped so as to accomplish the same task as the chisel, to apply force in two directions within the wood.
8. The correct answer is "d." A block and tackle can be simply constructed with two pulleys and a lifting line such as a rope, a chain, or a belt of some type.
9. The correct answer is "a." The vehicle transmission can be used to convert engine revolutions into torque increases or decreases. Torque increases result in a slowing of velocity or speed. Increasing torque by downshifting slows the vehicle down. Decreasing torque by shifting to a higher gear increases speed.
10. The correct answer is "a." Up shifting results in torque decreases and speed increases. You can feel the power and speed differences when a vehicle goes into "overdrive." Putting a vehicle in "overdrive" lowers the torque output but increases the speed. Overdrive is useful in driving on flat surfaces, but the vehicle may not produce enough torque to power it up a steep hill.