Explain what it means when we say a substance is magnetic.

Scientists are able to use body waves to determine what makes up the different layers of the Earth's interior. What characterist

k0ka [10]

Answer:

P-waves travel through liquids and solid while S-waves only travel through solids.

Explanation:

Scientists are able to use the fact that P-waves travel through both solids and liquids and waves travel through only solids to determine what makes the different layers of the Earth.

5 0

2 years ago

A 4.2-g bullet is fired at a speed of 370 m/s into a stationary lead block, which moves a distance of 1.2 m before coming to res

Natali5045456 [20]

Answer:

(a) F = 239.575 N (b) t = 0.00649s or 6.49 ms

Explanation:

(a) By law of energy conservation, the bullet kinetic energy will be transferred to work done on stopping it from moving.

Formula for Kinetic Energy $E_k = \frac{mv^2}{2}$ where m is bullet mass, v is the velocity

Formula for work $W = FS$ where F is the average force and S is the distance travelled.

$E_k = W$

$\frac{mv^2}{2} = FS$

$F = \frac{mv^2}{2S}$

Substitute m = 4.2 g = 0.0042 kg, v = 370 m/s and S = 1.2 (m)

$F = \frac{0.0042*370^2}{2*1.2} = 239.575 N$

(b) If the force is constant, since the mass is constant and F = ma according to Newton's 2nd law, the acceleration on bullet is also constant

$a = \frac{F}{m} = \frac{239.575}{0.0042} = 57041.67 (m/s^2)$

We also have $v(t) = v_0 + at$

At the time the bullet is coming to rest, $v(t) = 0, a = -57041.67 m/s^2$

Therefore, $0 = 370 - 57041.67t$

$t = \frac{370}{57041.67} = 0.00649 s = 6.49 ms$

3 0

4 years ago

A cart traveling at 0.3 m/s collides with stationary object. After the collision, the cart rebounds in the opposite direction. T

padilas [110]

Answer:

Explanation:

First case

A cart speed is 0.3m/s. i.e the initial velocity is u=0.3m/s

It collide with a stationary body, then after collision the ball rebounds and move in opposite direction. This shows that the ball have a velocity after impulse let say v

Then, impulse is given as the change in linear momentum of a body

Impulse =m∆v

I=m(v-u)

Note, momentum is a vector quantity.

I=m(v--u)

I=m(v+u)

I=m(v+0.3)

I¹=0.3m+mv. Equation 1

Second case

A cart speed is 0.3m/s. i.e the initial velocity is u=0.3m/s

It collide with a stationary body, then after collision the ball is at rest, this show that the final velocity is v=0

Then, impulse is given as the change in linear momentum of a body

Impulse =m∆v

I=m(v-u)

Note, momentum is a vector quantity.

I=m(v--u)

I=m(v+u)

In this case v=0 u=0.3m/s

I=m(0+0.3)

I²=0.3m. Equation 2

If we compare impulse 1 (I¹) to impulse 2 (I²)

Subtract equation 2 from 1

We have, I¹ - I² =0.3m+mv -0.3m

I¹ - I² =mv

I¹ =mv+I²

We notice that the first impulse (I¹) is greater than second impulse (I²) by mv.

The correct answer is A

5 0

3 years ago

A block of mass 5 kg is placed on a rough table having a coefficient of static friction μs = 0.2.What is the force required to m

just olya [345]

Answer:

<em>We need to (at least) apply a force of 9.8 N to move the block</em>

Explanation:

<u>Second Newton's Law</u>

If a net force $F_n$ different from zero is applied to an object of mass m, then it will move at an acceleration a, given by

$F_n=ma$

If we apply a force F to an object placed on a rough surface, the only way to make it move is to beat the friction force which is given by

$F_r=\mu F_N$

Where $\mu$ is the static friction coefficient and $F_N$ is the normal force exerted by the table to the object. Since there is no motion in the vertical direction the normal force equals the weight of the object: