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4 years ago

In which activity is no work done?

Physics

2 answers:

Doss [256]4 years ago

5 0

Answer: The correct option is B.

Explanation:

Work is done when the force is applied to move an object to certain distance.

In the case of lifting a book, the work is done as the force is applied to lift the book. There will be displacement.

In the case of holding a brick, no work is done as the force is applied in this case but there is no displacement.

In the case of climbing stairs, work is done in climbing the stairs as the force is acting here. There will be displacement when the man will climb.

In the case of pushing a shopping cart, the work is done as the force is applied to a shopping cart. There will be displacement in forward direction.

Therefore, the correct answer is B.

sleet_krkn [62]4 years ago

3 0

The answer is B because you are not using force or energy as if you were if you were to lift or push something.

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what will be the focal lenght of a combined lens made by contact of two lenses of power +3D and -2D.

4vir4ik [10]

P_1=+3D
P_2=-2D

$\\ \bull\tt\dashrightarrow P=P_1+P_2$

$\\ \bull\tt\dashrightarrow P=+3D-2D=+1D$

Now

$\\ \bull\tt\dashrightarrow f=\dfrac{1}{P}$

$\\ \bull\tt\dashrightarrow f=\dfrac{1}{1}$

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3 years ago

A pendulum of mass 5.0 ???????? hangs in equilibrium. A frustrated student walks up to it and kicks the bob with a horizontal fo

Rudiy27

Answer:

a. 37.75°

b. 6.21 m

Explanation:

a. The horizontal force acting on a pendulum bob is given as:

F = mgsinθ

where m = mass of bob

g = acceleration due to gravity

θ = angle string makes with the vertical or angle of displacement

Making θ subject of formula, we have:

θ = $sin^{-1}(\frac{F}{mg} )$

θ = $sin^{-1} (\frac{30}{5*9.8})$

θ = 37.75°

The maximum angle of displacement is 37.75°

b. Period of a pendulum is given as:

$T = 2\pi\sqrt{ \frac{L}{g} }$

where L = length of string

Therefore, making L subject of formula:

$L = \frac{gT^2}{4\pi^2}$

$L = \frac{9.8 * 5^2}{4\pi^2} \\\\\\L = 6.21 m$

The string holding the pendulum has to be 6.21 m long.

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