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gogolik [260]
3 years ago
14

In a ballistics test, a 28-g bullet pierces a sand bag that is 30cm thick. If the initial bullet velocity was 55 m/s and it emer

ged from the sandbag moving at 18m/s, what was the magnitude of the friction force (assuming it to be constant and the only force present) that the bullet experienced while it traveled through the bag
Physics
1 answer:
slega [8]3 years ago
6 0

Answer:

Explanation:

Given that,

The mass of the bullet is

M= 28g = 0.028kg.

Thickness oof sack bag

d = 30cm = 0.3m

Initial velocity of bullet Vi = 55m/s

Velocity at which the bullet emerges the sack bag is Vf = 18m/s

We want to calculate the frictional force present in the sack bag.

Using conservation of energy.

Work done by friction in the sack is equal to change in kinetic energy.

Work done by friction is given as

Wf = Fr × d

The distance is the thickness of the bag

Wf = Fr × 0.3

Wf = 0.3 • Fr

Change in kinetic energy is calculated by

∆K.E = ½mVf² — ½ mVi²

∆K.E = ½m(Vf² — Vi²)

∆K.E = ½ × 0.028 ( 18²-55²)

∆K.E = 0.014 × -2701

∆K.E = -37.814 J

Since

Work done by friction = ∆K.E

0.3 Fr = -37.814

Fr = -37.814/0.3

Fr = -126.05 N

The, negative sign show that frictional force is opposing the motion.

Fr = 126.05 N

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Answer:

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Explanation:

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Since all the points of the merry go round complete 1 circle in the same time, the angular velocity of each point of the merry go round is the same, and so all the points also have the same angular acceleration.

The tangential acceleration instead is given by

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where

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r is the distance from the centre of the merry go round

Since the girl is near the outer edge and the boy is closer to the centre, the value of r for the girl is larger than for the boy, so the girl has greater tangential acceleration.

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3 years ago
What is the net work on the block?
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8 0
3 years ago
How do I convert 200 yards into meters using Dimensional Analysis? Explain thoroughly. Thanks!
shtirl [24]

Explanation:

When doing this calculation manually, the formula of conversion that you need to use is yd / 1.0936 = m and this is the same formula used by the online calculator. For instance, 2yd = 1.83m and 15yd = 13.72m.

So 200 yards is (200 / 1.0936)

which is 182.88 Meters

Hope it helps..

8 0
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Three observers watch a train pull away from a station toward the right of the platform. Observer A is in one of the train’s car
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Observer A is moving inside the train

so here observer A will not be able to see the change in position of train as he is standing in the same reference frame

So here as per observer A the train will remain at rest and its not moving at all

Observer B is standing on the platform so here it is a stationary reference frame which is outside the moving body

So here observer B will see the actual motion of train which is moving in forward direction away from the platform

Observer C is inside other train which is moving in opposite direction on parallel track. So as per observer C the train is coming nearer to him at faster speed then the actual speed because they are moving in opposite direction

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Now as per Newton's II law

F = ma

Now if train apply the brakes the net force on it will be opposite to its motion

So we can say

- F = ma

a = \frac{-F}{m}

so here acceleration negative will show that train will get slower and its distance with respect to us is now increasing with less rate

It is not affected by the gravity  because the gravity will cause the weight of train and this weight is always counterbalanced by normal force on the train

So there is no effect on train motion



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3 years ago
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