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Strike441 [17]
3 years ago
9

For the following question, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the c

orrect answer to these questions from the codes (i), (ii), (iii) and (iv) as given below. i) Both A and R are true and R is correct explanation of the assertion. ii) Both A and R are true but R is not the correct explanation of the assertion. iii) A is true but R is false. iv)A is false but R is true. Assertion: Concave mirrors are used as reflectors in torches, vehicle head-lights and in search lights. Reason: When the object is placed beyond the centre of curvature of a concave mirror, the image formed is real and inverted.
please help

Physics
1 answer:
AleksandrR [38]3 years ago
5 0

Answer:

assertion is true but the reason is not true

Explanation:

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Consider the two-body situation at the right. A 300kg crate rests on an inclined plane and is connected by a cable to a 100 kg m
trasher [3.6K]

Answer:

a= 0.578 m/s

T = 1037.8 N

Explanation:

Data

m₁= 300 kg

m₂= 100 kg

inclined plane, θ =  30°

μk = 0.120

Newton's second law to m₁:

We define the x-axis in the direction parallel to the movement of the 300kg (m₁) crate on the ramp and the y-axis in the direction perpendicular to it.

∑F = m₁*a Formula (1)

Forces acting on m₁

W₁: m₁ weight : In vertical direction

N : Normal force : perpendicular to the inclined plane

f : Friction force: parallel to the inclined plane

T:  cable tension : parallel to inclined plane

Calculated of the W₁

W₁=m₁*g

W₁= 300kg* 9.8 m/s² = 2940 N

x-y weight components

W₁x= W₁sin θ =2940 N*sin(30)° =1470 N

W₁y= W₁cos θ =2940 N *cos(30)° =2156.4 N

Calculated of the N

We apply the formula (1)

∑Fy = m*ay    ay = 0

N - W₁y = 0

N = W₁y

N = 2156.4 N

Calculated of the f

f = μk* N= (0.120)*(2156.4 N)

f = 258.77 N

Newton's second law to m₁ in direction  x-axis :

∑Fx = m₁*ax   ,ax  =a

We assume that m₁ descends on the inclined plane and we positively take the direction of movement:

wx-f-T = m*a

wx - f - m*a =T

1470  -258.77 -300*a =T

T= 1211.23-300*a   Equation (1)

Newton's second law to m₂

∑Fy = m₂*ay   ,ay  =a

Forces acting on m₂

W₂: m₂ weight : In vertical direction

T:  cable tension:In vertical direction

Calculated of the W₂

W₂=m₂*g

W₂= 100kg* 9.8 m/s² = 980 N

∑Fy = m₂*a

Because we assume that m₁ descends on the inclined plane, then, m₂ ascends  vertically, we take positive the direction of movement:

T-W₂ = m₂*a

T-980 = 100*a

T = 980 + 100*a Equation (2)

Problem development

Equation (1) =  Equation (2) = T

1211.23-300*a= 980  + 100*a

1211.23- 980 = 100*a + 300*a

231.23 = 400*a

a= 231.23 / 400

a= 0.578 m/s

Because the acceleration tested positive then effectively m₁ descends on the inclined plane and m₂ ascends  vertically.

We replace a= 0.578 m/s in the equatión (2)

T = 980 + 100* (0.578 )

T = 1037.8 N

5 0
3 years ago
2. Kevin works as a janitor, and he is pushing a fully-
dybincka [34]

The time taken for him to move the bin 6.5 m is 2.30 s.

The given parameters;

  • <em>weight of the load, w = 557 N</em>
  • <em>force applied , F = 410 N</em>
  • <em>angle of force, =  15°</em>
  • <em>coefficient of kinetic friction  = 0.46</em>
  • <em>distance moved, d = 6.5 m</em>

The net horizontal force on the recycling bin is calculated as follows;

Fcos\theta - F_k = ma

where;

  • <em>m is the mass of the recycling bin</em>
  • <em />F_k<em> is the frictional force </em>

W = mg

557 = 9.8m\\\\m = \frac{557}{9.8} \\\\m = 56.84 \ kg

The net horizontal force on the recycling bin is calculated as;

Fcos \theta - F_k = ma\\\\Fcos\theta - \mu_kF_n  = ma\\\\410\times cos(15) \ - \ 0.46(557) = 56.84 a\\\\139.8 = 56.84a\\\\a = \frac{139.8}{56.84} \\\\a = 2.46 \ m/s^2

The time taken for him to move the bin 6.5 m is calculated as follows;

s = v_0t + \frac{1}{2} at^2\\\\6.5 = 0 + \frac{1}{2}  \times 2.46\times t^2\\\\6.5 = 1.23 t^2\\\\t^2 = \frac{6.5 }{1.23} \\\\t^2 = 5.285\\\\t = \sqrt{5.285} \\\\t = 2.30 \ s

Thus, the time taken for him to move the bin 6.5 m is 2.30 s.

Learn more here:brainly.com/question/21684583

7 0
3 years ago
What are the three stages of matter and how?​
n200080 [17]

Answer:

Solid, Liquid and Gas

Explanation:

They are the 3 states or stages of Matter

7 0
3 years ago
Describe a well-known hypothesis that was discarded because it was found to be untrue.earth-centered model of the universe. the
polet [3.4K]
The widely accepted hypothesis before that turned out wrong was the Earth-Centered theory or the Geocentric Theory. This was proposed by the philosopher Ptolemy. He came about to this hypothesis from hi observation that from the Earth's perspective, the celestial bodies like the Sun, stars and the moon, look like they rotate around the Earth each day and night. However, this was disproved by Galileo Galelei by his Heliocentric Theory. He observed through the telescope that the Venus also changes phases like the moon. However, he deduced that this is not possible from the positions of the Venus, Earth, Moon and Sun. 
6 0
3 years ago
The​ time, t, required to drive a fixed distance varies inversely as the​ speed, r. It takes 3 hr at a speed of 14 ​km/h to driv
kenny6666 [7]

Answer:

time taken with speed 23 km/h will be 1.8 hours or 1 hour 48 minutes

Explanation:

Given:

Time is inversely proportional to the speed

mathematically,

t ∝ (1/r)

let the proportionality constant be 'k'

thus,

t = k/r

therefore, for case 1

time = 3 hr

speed = 14 km/hr

3 = k/14

also,

for case 2

let the time be = t

r = 23 km/h

thus,

we have

t = k/23

on dividing equation 2 by 1

we get

\frac{t}{3}=\frac{k/23}{k/14}

or

t=\frac{14\times3}{23}

or

t = 1.8 hr = or 1 hour 48 minutes ( 0.8 hours × 60 minutes/hour = 48 minutes)

4 0
3 years ago
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