Question

A stone of 1 kg is thrown with a velocity of20 m/s across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. [a] what is the acceleration on the stone [b] what is the force of friction between the stone and ice? [c] how long it takes to come to rest? [d] If the same stone is thrown with a velocity of 40 m/s what will be the velocity at 50th meter? ,pls urgent for exams pls​

Answer 1

Answer:

We know the third equation of motion

v² = u² + 2as

Substituting the known values in the above equation we get,

0² = (20)² + 2(a)(50)

-400 = 100a

a = -400/100 = -4m/s² (retardation)

We know that

F = m×a

Substituting above obtained value of a = -4 in F = m x a we get,

F = 1 × (-4) = -4N

(Here the negative sign indicates the opposing force which is Friction)

Explanation:

please mark me as Brainliest

Answer 2

Answer:

[a] – 4m/s²

[b] – 4F

[c] 5secs

[d] 20√3m/s

Explanation:

According to the question :

• Mass of the stone : m = 21kg
• Initial velocity : u = 20m/s
• Distance travelled : s = 50m
• Final velocity : v = 0m/s

Let's find the [a] acceleration of the stone :

→ v² – u² = 2as

→ ( 0 )² – ( 20 )² = 2a ( 50 )

→ 0 – 400 = 100a

→ – 400 = 100a

→ – 400/100 = a

→ – 4m/s² = a

Therefore, the acceleration of the stone is – 4m/s².

Now, let's find the force (friction) between the stone and ice :

→ F = ma

→ F = 1 ( – 4 )

→ F = – 4N

Therefore, the friction between the stone and the ice is – 4N.

Let's now know how long it takes to come to rest :

→ v = u + at

→ 0 = 20 + ( – 4) t

→ 0 = 20 – 4t

→ 0 – 20 = – 4t

→ – 20 = – 4t

→ – 20/– 4 = t

→ 5secs = t

Therefore, it takes 5secs to come to rest.

If same stone is thrown with a velocity of 40m/s, what will be the velocity at 50m?

We know that :

• Mass of the stone : m = 1kg
• Initial velocity : u = 40m/s
• Distance travelled : s = 50m
• Final velocity : v = ?

Now, let's find the final velocity 'v' for the given situation :

→ v² – u² = 2as

→ v² – ( 40 )² = 2 ( – 4 ) ( 50 )

→ v² – 1600 = – 400

→ v² = – 400 + 1600

→ v² = 1200

→ v = √1200

→ v = √400 × 3

→ v = 20√3m/s

Therefore, the final velocity will be 20√3m/s.