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3 years ago

12

A boy walks towards a stationary plane mirror at a speed of 12ms^1 what is the relative speed of approach of the boy and his ima

ge? (a)zero (b)1.2ms^-1 (c) 2.4ms^-1 (d)1.44ms^-1

1 answer:

Vitek1552 [10]3 years ago

3 0

Answer:

a

Explanation:

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Does the coefficient of kinetic friction depend on speed?

kolbaska11 [484]

It depends on speed because it is a part of a car

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3 years ago

Why is it impossible to create a perpetual motion machine?

Tatiana [17]

Answer:

It is impossible to create a perpetual motion machine because some of the energy will always be lost in the conversion and therefore it will eventually stop.

Correct Answer : Option B

Explanation:

The perpetual motion machine is impossible machine as it is hypothetical working machine which would be in motion for an indefinite time in continuity of the motion. The continuity of motion for an indefinite time would mean that the working principle of the machine would never allow the dissipation of energy from the machine and all the machine would ultimately reserve all the energy and be converting it into forms without any loss.

This working principle is violation of first and second laws of thermodynamics and hence a machine will eventually lose some of its energy in every conversion of the working cycle and hence there will be a time where the machine would be stopped, and hence a perpetual motion machine cannot be made.

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3 years ago

What is the kinetic energy of a hammer that starts from rest and decreases its potential energy by 10 kJ?

erma4kov [3.2K]

Answer:

final kinetic energy of the hammer is 10 kJ

Explanation:

As we know that there is no non conservative force on the system

So here we can use the theory of mechanical energy conservation

So we will have

$\Delta K + \Delta U = 0$

here we know that

$\Delta U = - 10 kJ$

from above expression now

$K_f - K_i - 10 kJ = 0$

$K_f - 0 = 10 kJ$

so final kinetic energy of the hammer is 10 kJ

3 0

3 years ago

A small ball with a mass of 0.6 kg and a velocity of 12 m/s hits another ball with the same mass. The firs forward and hits a th

Ket [755]

I think is 30m/s I am not sure

8 0

3 years ago

If the coefficient of friction is 0.3900 and the cylinder has a radius of 2.700 m, what is the minimum angular speed of the cyli

Aleks04 [339]

Answer:

w=3.05 rad/s or 29.88rpm

Explanation:

k = coefficient of friction = 0.3900

R = radius of the cylinder = 2.7m

V = linear speed of rotation of the cylinder

w = angular speed = V/R or to rewrite V = w*R

N = normal force to cylinder

N= $=\frac{m(V)^{2}}{R}=m*(w)^2*R$

$Friction force\\Ff = k*N\\Ff= k*m*w^2*R$

$Gravitational force \\Fg = m*g$

These must be balanced (the net force on the people will be 0) so set them equal to each other.

$Fg = Ff$

$m*g = k*m*w^2*R$

$g=k*w^{2}*R$

$w^2 =\frac{g}{k*R}$

$w=\sqrt{\frac{g}{k*R}} \\w =\sqrt{\frac{9.8\frac{m}{s^{2}}}{0.3900*2.7m}}\\ w=\sqrt{9.306}=3.05 \frac{rad}{s}$

There are 2*pi radians in 1 revolution so:

$RPM=\frac{w}{2\pi }*60\\RPM=\frac{3.05\frac{rad}{s}}{2\pi}*60\\RPM= 0.498*60\\RPM=29.88$

So you need about 30 RPM to keep people from falling out the bottom

7 0

3 years ago