Phy101 Assignment No. 1 solution

PHYSICS (PHY101)

TOTAL MARKS: 20

Due Date: 18/04/2011

Question No. 1

If you have an umbrella, suddenly you have to face a rain storm with a strong wind, what determines the best position in which to hold an umbrella? Marks = 3

Answer:

The raindrops have a vertical velocity relative to the ground & you have a horizontal velocity when moving relative to the ground & so the raindrops can penetrate "under" the umbrella & wet your legs.

Question # 2

Does Newton‘s second law hold true for an observer in a car as it speeds up, slows down or rounds a corner?

Answer: Marks = 5

Yes it holds true. An inertial reference frame is one in which Newton's First Law of Motion, the Law of Inertia, holds true. In such a frame, objects which have no force acting on them move in straight lines, with constant speed. Any deviation from such a motion is presumed to be due to a force whose magnitude and direction can be deduced by applying Newton's Second Law of Motion, the Force Law, to observations of that deviation.

An observer who is at rest is in an inertial reference frame, and observers who are not at rest, but are moving with uniform (unchanging, straight-line) motion are also in inertial reference frames. Any acceleration, whether a change in speed, a change of direction (such as, in the example above, our motion around the Earth's axis of rotation), or both, puts observers who share in that acceleration in an ac The observer inside the car, however, tends to use the car as his reference frame, just the same as if it were still at rest, and since it is accelerating, will perceive things differently from the observer who really is at rest. celerated reference frame.

Question No. 3

A dripping water faucet steadily releases drops 1.0 s apart. As these drops fall, will the distance between them increase, decrease, or remain the same? Prove your answer. Mark 5Answer:By supposing above scenario we ll apply this equation Change in velocity= change in position /travel time According to this equation with the fall successively downward the average velocity will increase and hence the distance between them will also increase

Question # 4

The fastest measured pitched baseball left the pitcher’s hand at a speed of 55.0m/s. if the pitcher was in contact with the ball over a distance of 2.0m and produce constant acceleration,

(a) what acceleration did he give the ball, and

(b) How much time did it take him to pitch it?

Answer: Marks = 7

(a) What acceleration did he give the ball

2as= vf2-vi22

(a)(2)= (55)^2-(0)

4(a) = 3 025

(a)=3025/4

a=756.25 m/s^2

(b) How much time did it take him to pitch it

t = v - u / a

= 55-0/756.25

=55 sec