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3 years ago

Can you please help me?

Physics

2 answers:

Anika [276]3 years ago

5 0

Answer:

<h3>Law of reflection</h3>

Explanation:

According to the laws of reflection,

Incident ray, reflected ray and normal lie on the same plane.

Angle of reflection and angle of incidence are always equal.

→ Angle of reflection : Angle of which light rays reflect off surface.

→ Angle of incidence : Angle at which light rays strikes the surface.

insens350 [35]3 years ago

3 0

Answer: reflection

Explanation:

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The block of weight 113 lb is pushed with a force of P = 31 lb on top of two cylindrical rollers with a weight of 42 lb and a ra

Lilit [14]

Answer:

The block's speed will be of 5,1 ft/s

Explanation:

For this problem solve it is used the work and energy theorem which state:

$W=dK$

Where W is the net work done and dK the change in the kinetic energy between in the time after and before the force is applied. The net work can expressed as:

$W=F.d$

Here F and d are applied force and the displacement. While the kinetc energy for the i body:

$Ki=1/2*m_{1}V_{1}^2+1/2*I_{1}w_{1}^2$

Where mi,Ii Vi, wi are the mass, the moement of inertia, the linear and the angular velocity for the i body respectively. Therefore to calcule the total change in kinetic energy we take into account all the bodies involves, in this case the block and the two rollers. Assuming fixed rollers but can rotate, and the block with linear movement, the final kinect energy is:

$Kf=1/2*m_{b}V_{b}^2+1/2*I_{r1}w_{r1}^2+1/2*I_{r2}w_{r2}^2$

Note since at the beginning the bodies system is at rest hence the initial kinetic energy is null. In the above equation the subscripts b, r1 and r2 relate to the block and the two rollers.

For solid roller the moment of inertia can be calculated as:

$I_{r}=1/2*m_{r}R_{r}$

Where mr and Rr are the mass and radius rollers. Replacing the moment of inertia in the kinetic energy:

$Kf=1/2*m_{b}V_{b}^2+1/4*m_{r1}R_{r1}w_{r1}^2+1/4*m_{r2}R_{r2}w_{r2}^2$

As at the point of contact there is no displacement between the surfaces of the block and the rollers, in that point the linear velocities of this bodies are the same. So can expressed the linear velocity of the block as function of the rotating speed and the rollers radius:

$V_{b}=w_{r}R$

Entering latest in the new kinetic energy expression:

$Kf=1/2*m_{b}.(w_{r}.R)^2+1/4*m_{r}Rw_{r}^2+1/4*m_{r}Rw_{r}^2$

By doing this the kinetic energy expressed only as function of the roller rotating speed. As the roller rotatings speed are the same, and the masses and the radius are known, the the kinetic energy can expressed as:

$Kf=1/2*113\ lb.\1.57\ ft\ w^2+1/4*42\ lb.\ 1.57\ ft\ w^2+1/4*42\ lb.\ 1.57\ ft\ w^2$

$Kf=191\ lb.ft^2 w^2$

Before calculating the work, we will obtain the force in the proper units:

$F=30\ lbf\ *\ 32.16\frac{lb.ft/s}{lbf}$

$F=964.8\ lb.ft/s^2$

Then calculate the work:

$W=964.8\ lb.ft/s\ *\ 2.08\ ft$

$W=2006.8\ lb.ft^2/s^2$

By equating the work and kinetic energy equations and solving for the rotating speed:

$2008.8\ lb.ft^2/s^2=190\ lb.ft^2 w^2$

$w=\sqrt(\frac{2006.8\ lb.ft^2/s^2}{190\ lb.ft^2})$

$w=3.24 1/s$

And finally multiplying the roller rotating speed by the rollers radius, the block speed result:

$V=1.57 ft\ * 3.24 1/s$

$V=5.1 ft/s$

5 0

4 years ago

A ball whose mass is 0.3 kg hits the floor with a speed of 7 m/s and rebounds upward with a speed of 4 m/s. if the ball was in c

Maurinko [17]

Newton's second law is stated as:
F=ma,

a = (7-4)/1.5 = 2 m/s^2 (it is a deceleration due to impact with floor. And thus the ball exerts force on the floor).

Therefore,

F= 0.3*2 = 0.6 N

8 0

3 years ago

Example of kinetic energey

liubo4ka [24]

Answer:

rolling ball down a hill

Explanation:

A rolling ball has kinetic energy

5 0

3 years ago

Read 2 more answers

How do Newton's three laws of motion explain the movement of people and objects around you?

Sunny_sXe [5.5K]

Answer:

Newtons first law-An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force

Newtons second law-The acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object

Newtons third law-For every action, there is an equal and opposite reaction

Explanation:

1- Imagine a ball rolling down the hill,it will be moving down unless something stops it. and the ball stops, unless you or an unbalanced force acts it will be at rest

2-If you use the same force to push a truck and push a car, the car will have more acceleration than the truck, because the car has less mass.  It is easier to push an empty shopping cart than a full one, because the full shopping cart has more mass than the empty one.

3-If I kick my friend he will also kick me back. Better example-when you jump, your legs apply a force to the ground, and the ground applies and equal and opposite reaction force that propels you into the air. Engineers apply Newton's third law when designing rockets and other projectile devices.

3 0

3 years ago

A circular turntable rotates at constant angular velocity about a vertical axis. There is no friction and no driving torque. A c

7nadin3 [17]

Answer:

the moment of inertia of the water increases, therefore the angular velocity must decrease

Explanation:

To analyze this exercise we see that the system is isolated therefore the angular momentum is conserved

initial instant. The plate with the ice cap (solid)

L₀ = I₀ w₀

where Io is the moment of inertia of the plate plus the ice disk

I₀ = ½ M r² + ½ m r²

where M is the mass of the plate and m is the mass of the ice

final instant. When the ice has melted, therefore we have water that is a liquid and as the system is rotating it accumulates towards the periphery of the system,

L_f = I w

in this case the moment of inertia is

I = ½ M r² + I_water

the moment of inertia of water if it is concentrated in a thin ring is

I_{water} = mr²

we can see that the moment of inertia increases

how angular momentum is conserved

L₀ = L_f

(½ M r² + ½ m r²) w₀ = (½ M r2 + I_{water}) w

w = $\frac{ \frac{1}{2} Mr^2 + \frac{1}{2} m r^2 }{\frac{1}{2} Mr^2 + I_{water} } \ w_o$ w

we can see that the moment of inertia of the water increases, therefore the angular velocity must decrease

3 0

3 years ago