Free SIFT Mechanical Comprehension Questions and Answers 1 — Questions and Answers

Question 1: Christian takes thirty steps forward, followed by thirty steps backward. In terms of his total distance, how many steps has Christian taken?

35
40
60 (Correct answer)
30

Correct answer: 60

The question asks for Christian's total distance, which refers to the entire length of the path he traveled, regardless of direction. Christian took thirty steps forward and then thirty steps backward. Therefore, his total distance covered is the sum of these two movements: 30 steps + 30 steps = 60 steps. This is distinct from displacement, which would be zero since he returned to his starting point.

Question 2: Danny, a young man from the Northern Hemisphere, is positioned on a scale. Danny is 20 kg heavy. In Newtons, the scale readout is shown. What is Danny's readout?

190
194
196 (Correct answer)
198

Correct answer: 196

Weight is a force, measured in Newtons, and is calculated by multiplying an object's mass by the acceleration due to gravity (g). The acceleration due to gravity on Earth is approximately 9.8 meters per second squared (m/s²). Therefore, Danny's weight is 20 kg * 9.8 m/s² = 196 Newtons. The scale readout would display this force.

Question 3: An inclined plane's strength increases as its

Output
Mechanical Advantage (Correct answer)
Power
None of the Above

Correct answer: Mechanical Advantage

An inclined plane's 'strength' in terms of making work easier is its ability to reduce the effort force required to move an object. This is quantified by its mechanical advantage. A higher mechanical advantage means that a smaller input force is needed to overcome a larger resistance force, effectively increasing the ease or 'strength' of the simple machine.

Question 4: The mechanical advantage of a lever with 250 N of resistance and 50 N of effort is

0.2
0.5
5 (Correct answer)
1

Correct answer: 5

Mechanical advantage (MA) is calculated as the ratio of the resistance force (output force) to the effort force (input force). In this case, the resistance force is 250 N and the effort force is 50 N. Therefore, the mechanical advantage is 250 N / 50 N = 5. This means the lever multiplies the applied effort by a factor of 5.

Question 5: 2 m are raised by a 50 N vase. What work is completed?

100J (Correct answer)
25J
2J
50

Correct answer: 100J

Work is defined as the product of the force applied to an object and the distance over which that force is applied in the direction of motion. In this scenario, the force required to raise the vase is its weight, 50 N, and the distance it is raised is 2 m. Therefore, the work completed is 50 N * 2 m = 100 Joules.

Question 6: The sliding coefficient of friction for a brick is 0.28. The book must be forced to slide at a constant speed with a force of 5.5 N. What is the brick's mass?

2.8 kg
1 kg
5.5 kg
2.0 kg (Correct answer)

Correct answer: 2.0 kg

When an object slides at a constant speed, the applied force equals the force of kinetic friction. The force of kinetic friction (Ff) is calculated as the coefficient of kinetic friction (μk) multiplied by the normal force (Fn), where Fn for a horizontal surface is mass (m) times gravity (g). So, Ff = μk * m * g. Rearranging to solve for mass: m = Ff / (μk * g). Plugging in the values (Ff = 5.5 N, μk = 0.28, g ≈ 9.8 m/s²), we get m = 5.5 / (0.28 * 9.8) ≈ 2.0 kg.

Question 7: A basic machine always has

50% efficiency
200% efficiency
<100% efficiency (Correct answer)
100% efficiency

Correct answer: <100% efficiency

All real-world machines experience some energy loss, primarily due to friction, heat, and sound. This means that the useful work output of any machine will always be less than the total energy or work input. Consequently, the efficiency of any basic machine, or any machine for that matter, will always be less than 100%.

Free SIFT Mechanical Comprehension Questions and Answers 1

Christian takes thirty steps forward, followed by thirty steps backward.
In terms of his total distance, how many steps has Christian taken?