1. A cup filled up with water is steadily slided towards a barrier. What will happen when the cup hits the barrier? Explain your answer with the help of a rough sketch. (2) 2. A clock having marks instead numbers on its dial appears to indicate 7.25 when viewed in a plane mirror. What is the correct time? Explain your answer. (2) 3. A point object O is kept between two parallel mirrors in such a way that it is 4 cm from the left mirror and 5 cm from the right mirror. Find the distance between the second images formed. Also draw a rough sketch. (2) 4. An athlete prefers to find on sand instead of hard floor while taking a high jump. Explain. (2) 5. An object is 20 cm away from a plane mirror. How far the image shifts from its previous position (a) if the mirror is moved 7 cm away from the object. (b) if the object is moved 7 cm towards the mirror. 6. A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet. (3) 7. State Newton's Universal law of gravitation. Discuss the importance of this law. (3) 8. Draw a ray diagram to show the image formation when two plane mirrors are kept perpendicular to each other. (3)
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A hypothesis is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous observations that cannot satisfactorily be explained with the available scientific theories
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q8⭎⭎
__________
q=6⤵
q(6) = When the stone from the top of the tower is thrown,
Initial velocity u = 0
Distance travelled = x
Time taken = t
Therefore,
Height, h = (100 – x)
Initial velocity, u = 0
Time, t =?
g = 10 m/s2 (As the stone is falling down)
We know that,
h= ut+1/2gt2
Substituting the values in above equation
(100 – x) = 0 × t +1/2× 10 × t2
(100 – x) = 5t2 (i)
(ii)Now, for stone projected vertically upwards:
Height, h = x
Initial velocity, u = 25 m/s
Time, t =?
g = -10 m/s2 (Because the stone is going up)
We know that,
s= ut+1/2gt2
(100 – S) = 25t + 1/2 (-10) t²
= 25t – 5t²
On adding the above equations We get
100 = 25t
or t = 4 s
After 4sec, two stones will meet
From (a)
x = 5t2 = 5 x 4 x 4 = 80m.
Putting the value of x in (100-x)
= (100-80) = 20m.
This indicates that after 4seconds, 2 stones meet a distance of 20 m from the ground.
(i) When the stone from the top of the tower is thrown,
Initial velocity u = 0
Distance travelled = x
Time taken = t
Therefore,
Height, h = (100 – x)
Initial velocity, u = 0
Time, t =?
g = 10 m/s2 (As the stone is falling down)
We know that,
h= ut+1/2gt2
Substituting the values in above equation
(100 – x) = 0 × t +1/2× 10 × t2
(100 – x) = 5t2 (i)
(ii)Now, for stone projected vertically upwards:
Height, h = x
Initial velocity, u = 25 m/s
Time, t =?
g = -10 m/s2 (Because the stone is going up)
We know that,
s= ut+1/2gt2
(100 – S) = 25t + 1/2 (-10) t²
= 25t – 5t²
On adding the above equations We get
100 = 25t
or t = 4 s
After 4sec, two stones will meet
From (a)
x = 5t2 = 5 x 4 x 4 = 80m.
Putting the value of x in (100-x)
= (100-80) = 20m.
This indicates that after 4seconds, 2 stones meet a distance of 20 m from the ground.
_________
q=5⤵
Initially, the object is placed 20 cm in front of mirror. So the image will form 20 cm behind the mirror.
If mirror is moved 2 cm towards the object,
distance between object and mirror = 20 cm - 2 cm = 18 cm
distance between mirror and image = 18 cm, which is 2 cm less than the initial case.
Since, the mirror has also moved 2 cm away from the position of original image, so the total distance between the positions of the original and final images is 2 cm + 2 cm = 4 cm
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