Question

1. The result of difference of two forces 1N each acting on a body can be (in newton) (b) 2 (c) 1 (d) 2 sin(0/2) (a) O

2. A body is projected from the ground at angle of 30°. At the highest position of the projectile motion, the angle between velocity and acceleration of the body is (a) 00 (b) 450 (c) 90° (d) 180°

3. A force of 20 N is acting on 10 kg box to make it move on a straight horizontal road with a constant speed. The acceleration produced in the box is (a) 0 (b) 2 ms (c) 0.5 ms? (d) 200 ms

4. The escape velocity of a man on the earth surface is (a) 1.12 km/s (b) 11.2 m/s (c) 11.2 Km/s (d) 17.0 Km/s

5. A ball accelerates at rate of 4 ms - from the rest and the retards at 3 ms to come to rest. If the total time taken is 7 seconds, its total displacement is (a) 0 m (b) 42 m (c) 21 m (d) 84 m

6. Which mirror is used in the rear view of a vehicle? (a) plane mirror (b) concave mirror (C) convex mirror (d) elliptical mirror​

Answer 1

1. (a) 0

6. Convex mirrors

4. 11.2 km/s

Answer 2

Answer:

1. The required result will be = 0 N

2. The answer is  = 90°

3. The acceleration produced in the box = 2 m/s²

4. The escape velocity will be = 11.2 km/s

5. the total displacement  = 84m

6. The required answer is Convex Mirror.

Explanation:

For solution 1,

It is given that both the forces are of 1N each.

Let F₁ be one force and F₂ be the another force, so the result of the difference between these two forces will be = Fnet = F₁ - F₂ = 1 - 1 = 0N

For solution 2,

It is said that the body is projected at an angle of 30°

But we know that at the highest point the angle between the acceleration and the velocity of hat particular body is always 90°, because the vertical component at the peak is of velocity is always 0.

For solution 3,

It is given to us that the Force, F = 20N

mass, m = 10kg

Therefore we know that the acceleration, a = $\frac{F}{m}$ = 20/10 = 2m/s²

For solution 4,

the escape velocity will always be nearly equal to 11.2 km/s, because the original escape velocity  = 11.186 km/s

It comes from the formula : v² = $\frac{2GM}{d}$

where v = escape velocity

G =  gravitational constant = 6.67 x 10⁻¹¹ m³kg⁻¹s⁻²

M = mass of the body

d = radius

For solution 5,

it is given that the acceleration  = 4m/s² and retardation = 3 m/s²

let the time be t₁ and t₂ for acceleration and retardation respectively.

therefore,

t₁ = $\frac{v- u}{a}$ = $\frac{v - 0}{4}$ = $\frac{v}{4}$

t₂ = $\frac{v - u}{a}$ = $\frac{0 - v}{-3}$ = $\frac{v}{3}$

According to the question,

total time = 7

or, t₁ + t₂ = 7

or, $\frac{v}{4}$ + $\frac{v}{3}$ = 7

or, v = 12 m/s

Since we need to find the displacement,

so, we know that S = vt

where S = displacement

v = velocity

t = time

Therefore, S = 7 x 12 = 84m

For solution 6,

Convex mirror is used as rear view mirror since they give erect images and also has a clear view of the curved surfaces.

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