If rain falls against the direction of walking, how must a pedestrian tilt their umbrella ________________________?
Show answer Hide answer
Answer: D. less inclined when standing
Explanation
Walking into rain causes the relative velocity vector of the raindrops to tilt forward relative to a stationary observer. Standing still means the rain falls more vertically, requiring a different tilt angle for complete coverage. Vector addition of the walking velocity and falling rain velocity proves that movement changes the required umbrella angle. Relative velocity is a fundamental concept in classical kinematics describing motion from different reference frames. The apparent direction of precipitation depends entirely on the speed and direction of the moving observer. Vector triangles are used to solve relative motion problems involving wind, rain, and moving vehicles.
Option A is incorrect because moving requires tilting the umbrella less forward compared to standing still. Option B suggests the correct behavior during motion but does not answer the comparison to standing. Option C incorrectly claims that a stationary person needs a more inclined umbrella than a moving person.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. When scavenge air is delivered to a two-stroke engine at a higher density than the surrounding air, the engine is classified as__________________?
Show answer Hide answer
Answer: B. Not supercharged
Scavenge air delivered at a higher density than surrounding ambient air through a compressor means the engine is supercharged.
Q2. Up to what point does Hooke’s law remain valid for elastic materials____________________?
Show answer Hide answer
Answer: B. limit of proportionality
Hooke law remains strictly valid for elastic materials up to the limit of proportionality. Beyond this specific stress point, the linear relationship between stress and strain ceases. Engineering calculations rely on thi...
Q3. Coulomb friction describes the frictional resistance acting between_____________________?
Show answer Hide answer
Answer: A. bodies having relative motion
Coulomb friction describes the frictional resistance encountered between solid bodies having relative motion. This classical friction model assumes that the frictional force is proportional to the normal force pressing t...
Q4. In which type of structural configuration is a diamond riveted joint typically applied _____________________?
Show answer Hide answer
Answer: A. butt joint
Diamond riveted joints feature tapered or triangular rivet arrangements that are ideally suited for connecting structural butt joints. This specialized geometry provides progressive load distribution across multiple cove...
Q5. If three coplanar forces maintain static equilibrium on a rigid body, what geometric condition must they satisfy___________________?
Show answer Hide answer
Answer: D. all the above are correct
Three coplanar forces in static equilibrium must be either all parallel or concurrent. Concurrency at a single point ensures that the resultant moment about that point equals zero. Parallel force systems achieve equilibr...
Q6. Roughly, what is the ratio of the ultimate shear strength of steel compared to its tensile strength_________________?
Show answer Hide answer
Answer: B. half
The ultimate shear strength of structural steel is approximately half of its ultimate tensile strength. Empirical testing consistently confirms that structural steels resist pure shear stresses up to roughly fifty percen...