Could anyone can help me for this question I don’t understand how I can do?!! Please it really important!!

Three students have been studying relative motion and decide to do an experiment to demonstrate their knowledge. The experiment

miskamm [114]

Answer with Explanation:

We are given that

Constant speed of Jane=12.6 m/s

a.When Fred can throw the ball 30 m/s

We have to find the angle relative to the horizontal when he throw the ball in order for Sue to see the ball travel vertically upward.

Let $\theta$ be the angle .

Therefore,

$30 cos\theta=12.6$

$cos\theta=\frac{12.6}{30}=0.42$

$\theta=cos^{-1}(0.42)=65.165^{\circ}$

b.We have to find the height to which ball reach.

$v^2-v^2_0=2aS$

$S=\frac{v^2-v^2_0}{2a}=\frac{0-(30 sin65.165)^2}{2(-9.81)}$

$S=37.78 m$

7 0

3 years ago

A 300W hot plate produces 45,000 J of thermal energy while operating for 2 min. What is the efficiency of this devide? it need t

Gekata [30.6K]

Answer:

Explanation: P = 300 W and t = 2 min = 120 s

Energy Q = Pt = 300 W · 120 s = 36 000 J.

Thus, plate can not produce 45 000 J heat.

5 0

3 years ago

If he leaves the ramp with a speed of 35.0 m/s and has a speed of 33.0 m/s at the top of his trajectory, determine his maximum h

nadezda [96]

Answer:

H = 6.93 m

Explanation:

given data

velocity v = 35 m/s

horizontal component Vx = 33 m/s

solution

we get here maximum height so first we get vertical component here that is express as

Vy = $\sqrt{v^2- Vx^2}$ .........................1

put here value

Vy = $\sqrt{35^2- 33^2}$

Vy = 11.66 m/s

and

now we get height

H = $\frac{Vy^2}{2g}$ .............................2

put here value

H = $\frac{11.66^2}{2\times 9.8}$

H = 6.93 m

7 0

3 years ago

An 1100kg car reached 30m/s in 9s from rest. What force did the engine provide?

malfutka [58]

Answer:

≅3666.67 N

Explanation:

Use Newton's 2nd law, F = ma where F=force applied, m = mass of the object,

a = acceleration acquired by the object.

a= (v-u)/t where v = final velocity, u = initial velocity and t = time taken

calculate a = (30-0)/9 ≅ 3.33 m/s2

Then F = 1100×a = 3666.67 N

3 0

3 years ago

True or false?

Ksju [112]

1. False

Explanation: it's exactly the opposite. In fact, Lenz's law states that the induced current and the induced emf in a conductor are generated in such a direction that opposes to the change in magnetic flux through the coil. This is summarized by the negative sign in the Faraday's Newmann Lenz law:

$\epsilon= -\frac{d\Phi }{dt}$

where $\epsilon$ is the emf induced and $\frac{d\Phi}{dt}$ is the rate of change of magnetic flux through the coil.

Lenz's law is a consequence of the law of conservation of energy. In fact, we have:

- If the magnetic flux through a coil is increasing, then the induced current has a direction such that the magnetic field generated by the coil is opposite to the direction of the external magnetic field, in order to decrease the total flux

- If the magnetic flux through a coil is decreasing, then the induced current has a direction such that the magnetic field generated by the coil is in the same direction as the external field, in order to increase the total flux

2. False

Explanation: the magnetic flux through a surface is given by

$\Phi = BA cos \theta$

where

B is the magnitude of the magnetic field

A is the surface area

$\theta$ is the angle between the direction of B and the normal vector to the surface

As we see, the magnetic flux depends not only on B and A, but also on the orientation of the coil with respect to the magnetic field.

3. False

Explanation:

- Sound waves are mechanical waves: mechanical waves are waves consisting of oscillations of the particles in a medium. Due to their nature, therefore, mechanical waves can propagate only in the presence of a medium

- Electromagnetic waves are NOT mechanical waves: they consist of oscillations of electric and magnetic fields, in a direction perpendicular to the direction of propagation of the wave. Since em waves are not mechanical waves, they do NOT need a medium to propagate, since they can also travel through a vacuum; therefore the original statement is false.

5 0

3 years ago