Siruis, the brightest star in the night sky, has a luminosity of 22. This means that Sirius: A, B, C, D QUESTION

What determines whether an object will scatter light or reflect light?

Lady bird [3.3K]

Scatter light doesn't reflect, reflect light goes off a mirror.

4 0

3 years ago

A girl of mass m1=60 kilograms springs from a trampoline with an initial upward velocity of v1=8.0 meters per second. At height

AleksandrR [38]

a) 5.0 m/s

This first part of the problem can be solved by using the conservation of energy. In fact, the mechanical energy of the girl just after she jumps is equal to her kinetic energy:

$E_i=\frac{1}{2}m_1v_1^2$

where m1 = 60 kg is the girl's mass and v1 = 8.0 m/s is her initial velocity.

When she reaches the height of h = 2.0 m, her mechanical energy is sum of kinetic energy and potential energy:

$E_f = \frac{1}{2}m_1 v_2 ^2 + m_1 gh$

where v2 is the new speed of the girl (before grabbing the box), and h = 2.0m. Equalizing the two equations (because the mechanical energy is conserved), we find

$\frac{1}{2}m_1 v_1^2 = \frac{1}{2}m_1 v_2 ^2 + m_1 gh\\v_1^2 = v_2^2 +2gh\\v_2 = \sqrt{v_1^2 -2gh}=\sqrt{(8.0 m/s)^2-(2)(9.8 m/s^2)(2.0 m)}=5.0 m/s$

b) 4.0 m/s

After the girl grab the box, the total momentum of the system must be conserved. This means that the initial momentum of the girl must be equal to the total momentum of the girl+box after the girl catches the box:

$p_i = p_f\\m_1 v_2 = (m_1 + m_2) v_3$

where m2 = 15 kg is the mass of the box. Solving the equation for v3, the combined velocity of the girl+box, we find

$v_3 = \frac{m_1 v_2}{m_1 + m_2}=\frac{(60 kg)(5.0 m/s)}{60 kg+15 kg}=4 m/s$

c) 2.8 m

We can use again the law of conservation of energy. The total mechanical energy of the girl after she catches the box is sum of kinetic energy and potential energy:

$E_i = \frac{1}{2}(m_1+m_2) v_3^2 + (m_1+m_2)gh=\frac{1}{2}(75 kg)(4 m/s)^2+(75 kg)(9.8 m/s^2)(2.0m)=2070 J$

While at the maximum height, the speed is zero, so all the mechanical energy is just potential energy:

$E_f = (m_1 +m_2)gh_{max}$

where h_max is the maximum height. Equalizing the two expressions (because the mechanical energy must be conserved) and solving for h_max, we find

$E_i = (m_1+m_2)gh_{max}\\h_{max}=\frac{E_i}{(m_1+m_2)g}=\frac{2070 J}{(75 kg)(9.8 m/s^2)}=2.8 m$

4 0

4 years ago

What does "doing work" mean when it comes to physics?

kicyunya [14]

I think it means doing work in physics

4 0

3 years ago

What is meant by the statement '' density of water is 1000 kilograms per cubic metre ''?

LenKa [72]

It means that if you had a cubic meter of water it would weigh 1000 kilograms

4 0

4 years ago

If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy.

Alina [70]

If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy. It is a true statement .

Kinetic energy is the energy that an object possesses due to its motion. It is basically the energy of mass in motion. Kinetic energy can never be negative and it is a scalar quantity i.e. it provides only the magnitude and not the direction.

According to law of conservation of mechanical energy change in potential energy is equal and opposite to the change in the kinetic energy.

According to the principle of conservation of mechanical energy, The total mechanical energy of a system is conserved i.e., the energy can neither be created nor be destroyed; it can only be internally converted from one form to another if the forces doing work on the system are conservative in nature.

since, potential energy is stored in the form of work done

Work done = Fs cos (theta)

If force always acts perpendicular to an object's direction of motion

theta = 90 °

cos (90 ) = 0

Work done = 0

since , there is no work done , hence kinetic energy will not change

To learn more about kinetic energy here

brainly.com/question/12669551

#SPJ4

7 0

2 years ago