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Physics 1 Marks Question

Laws of Motion · UP Board (UPMSP) STD 11 Science (UPMSP - English Medium). 4 questions.

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Question 11 Mark
Why does a child feel more pain when she falls down on a hard cement floor, than when she falls on the soft muddy ground in the garden?
Answer
The effect of force F = ma. i.e., if the mass is constant for a system to decrease force, the ‘a’ should be decreased $\text{a}=\frac{(\text{v}-\text{u})}{\text{t}}$ initial and final velocity of falling body on a surface are u and zero. so it cannot be changed. If time during hitting is increased, the acceleration decreased and force will decrease.
On cemented hard floor the time to stop after fall on it is very-very small. But when she/he falls on soft ground of garden she/ he sinks in ground and takes more time to stop hence smaller force or pain acts on her/ him.
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Question 21 Mark
Why are mountain roads generally made winding upwards rather than going straight up?
Answer
On an inclined plane force of friction on a body going upward is $\text{f}_\text{s}=\mu\text{N}\cos\theta$ where $\theta$ is angle of inclination of a plane with horizontal if $\theta$ is small, the force of friction is high and there is a less chance of skidding.
The road straight up would have a larger angle and smaller would be the value of friction, hence more are the chances of skidding.
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Question 31 Mark
In the above given problem if the lower thread is pulled with a jerk, what happens?
Answer
Thread CD will break up if CD is pulled with the jerk because pull on thread CD is not transmitted from CD to AB by mass 2kg due to its inertia of rest.
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Question 41 Mark
Why are porcelain objects wrapped in paper or straw before packing for transportation?
Answer
Porcelain (or glass) objects are brittle in nature and can crack even small jerk on it. During transportation sudden jerks or even fall takes place.
When objects are packed in paper or straw etc.
The objects takes more time to stop or change velocity during jerks (due to breaks, or uneven road) so acceleration $\frac{(\text{v}-\text{u})}{\text{t}}$ decreased. So the force on objects will be smaller and objects become safer.
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