Question

answer the 25th, 26th and 27th question

27th question in English:

four students determine the velocity of a pulse in a slinky. They found that the pulse took 7.5 seconds to complete 3 times the length of the slinky which is 15 metre .the velocity of the pulse is calculated by them is :
a.6.5m/s
b.6.0m/s
c.7.5m/s
d.3.5m/s

Answer 1

Hi there !!

Q.27 )

Here we are asked to calculate the velocity of the pulse.

We are given the time taken by the pulse go to 3 times the distance of the slinky , that is 7.5 seconds


Therefore ,
Time taken by the pulse to complete 1 time the distance of the slinky = 7.5 / 3
= 2.5 sec


Velocity (speed ) = Distance / time


Distance = length of the slinky = 15 m

Velocity = 15 / 2.5
= 6 m/s
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Q.25

Option A is correct ] Straight line.

This is because the angle of incidence and angle of reflections are same.

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Q.26

Pressure is inversely proportional to Area.
This means that when area decreases,
pressure increases. Also , when area increases , pressure decreases.

So , here in this case we are asked to find the maximum pressure .This means that we also have to find which is the smallest area.

SO , the less pressure area is breadth x height [ 5 x 2 cm ]

mass = 2 kg

g = 10 m/s
Thrust = force = mg
= 2 x 10 = 20 N

Area = 5 cm x 2 cm
= 10 cm² = 0.001 m²


Pressure = Thrust ÷ Area
= 20 ÷ 0.001
= 20000 N/m⁻²

Therefore , option B is correct