The focal length for a convex lens is

A 15-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. what is the magnitude of the minimum force, applie

Juliette [100K]

In order to lift the child off the ground, the torque applied on the other side of the pivot must be equal to the torque produced by the child.

The torque of the child around the pivot is:
$\tau=(mg) d$
where m=15 kg is the mass of the child, g is the gravitational acceleration, d=1.5 m is the distance between the child and the pivot. So, we have
$\tau= (15 kg)(9.81 m/s^2)(1.5m)=220.7 Nm$

The torque on the other side of the pivot must be equal:
$\tau = 220.7 Nm$
and in this case, the force is applied at a distance of d=0.30 m from the pivot, therefore the intensity of the force must be
$F= \frac{\tau}{d}= \frac{220.7 Nm}{0.30 m}=735.7 N$

8 0

3 years ago

Read 2 more answers

PLEASE HELP ME I AM TIMED!

cupoosta [38]

I believe the answer is D

3 0

3 years ago

A 0.07-kg lead bullet traveling 258 m/s strikes an armor plate and comes to a stop. If all of the bullet's energy is converted t

Lubov Fominskaja [6]

Answer:

temperature change is 262.06°K

Explanation:

given data

mass = 0.07 kg

velocity = 258 m/s

to find out

what is its temperature change

solution

we know here

heat change Q is is equal to kinetic energy that is

KE = 0.5 × m× v² ...........1

here m is mass and v is velocity

KE = 0.5 × 0.07 × 258²

KE = 2329.74 J

and we know

Q = mC∆t .................2

here m is mass and ∆t is change in temperature and C is 127J/kg-K

so put here all value

2329.74 = 0.07 × 127 × ∆t

∆t = 262.06

so temperature change is 262.06°K

7 0

3 years ago

A capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a batte

vovikov84 [41]

<h2>Answer:</h2>

(e) halved

<h2>Explanation:</h2>

The electrical enery (E) stored in a capacitor is related to its capacitance (C) and potential difference (V) as follows;

E = $\frac{1}{2}$ x C x $V^{2}$ ------------------------(i)

Also, the capacitance (C) of a capacitor consisting of parallel plates is related to the area (A) of the plates and distance (d) between the plates as follows;

C = A x ε₀ / d ------------------------(ii)

Where;

ε₀ is the permittivity of free space.

Substituting equation (ii) into equation (i) gives;

E = $\frac{1}{2}$ x A x ε₀ / d x $V^{2}$ --------------------(iii)

From equation(iii)

When the potential difference (V) is constant, then the electrical energy (E) stored is <em>inversely </em>proportional to the distance between the plates. i.e

E = k / d ----------------(iv)

Where;

k = proportionality constant = $\frac{1}{2}$ x A x ε₀ x $V^{2}$ (which is the product of all constants)

Therefore from equation (iv);

=> E₁ x d₁ = E₂ x d₂ ---------------------------(v)

Where;

E₁ and E₂ are the initial and final values of the electrical energy stored.

d₁ and d₂ are the initial and final values of the distance between the plates.

<em>So, when the distance is doubled, i.e.</em>

d₂ = 2 x d₁

<em>Substitute the value of d₂ into equation (v) to give;</em>

=> E₁ x d₁ = 2 x d₁ x E₂

<em>Divide through by d₁ to give;</em>

=> E₁ = 2 x E₂

<em>Make E₂ subject of the formula</em>

=> E₂ = $\frac{1}{2}$ x E₁

Therefore, the electrical energy stored in the capacitor will be halved.

6 0

4 years ago

A car goes from rest to a speed of 90 km/h in 10 seconds . What is the car's acceleration in m/s²

zloy xaker [14]

First you must convert Km/hr to m/s. 90 km/hr equals 25m/s (this can be done through a conversion table by plugging in the conversion values). Then you need to see what was given:
vi (initial velocity)= 0m/s
vf (final velocity= 25m/s (90km/hr)
t (time)= 10s

Next you should find an equation that requires only the values you know and gives you the value you're looking for. Sometimes that requires two equations to be used, but in this case you only need one. The best equation for this would be a=(vf-vi)/t. Finally, plug in your values (a=(25-0)/10) to get your answer which would be 2.5m/s^2. Hope this helped!

7 0

3 years ago