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Vesna [10]
3 years ago
9

If only an external force can change the velocity of a body, how can the internal force of the brakes bring a car to rest? 1. It

is the driver, not the car itself who causes the breaking, so it is an external force. 2. The engine is stopped, so the car has no force to run further. 3. Some internal forces can change the velocity of a body. 4. It is the force of the road on the tires (an external force) that stops the car.
Physics
1 answer:
RoseWind [281]3 years ago
3 0

Answer:

4. It is the force of the road on the tires (an external force) that stops the car.

Explanation:

If there is no friction between the road and the tires, the car won't stop.

You can see this, for example, when there is ice on the road. You can still apply the brakes (internal force), but since there is no friction (external force) the car won't stop.

The force of the brakes on the wheels is not what makes the car stop, it is the friction of the road against still tires that makes it stop.

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A 90 kg person stands at the edge of a stationary children's merry-go-round at a distance of 5.0 m from its center. The person s
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Answer:

\omega = 0.016\,\frac{rad}{s}

Explanation:

The rotation rate of the man is:

\omega = \frac{v}{R}

\omega = \frac{0.80\,\frac{m}{s} }{5\,m}

\omega = 0.16\,\frac{rad}{s}

The resultant rotation rate of the system is computed from the Principle of Angular Momentum Conservation:

(90\,kg)\cdot (5\,m)^{2}\cdot (0.16\,\frac{rad}{s} ) = [(90\,kg)\cdot (5\,m)^{2}+20000\,kg\cdot m^{2}]\cdot \omega

The final angular speed is:

\omega = 0.016\,\frac{rad}{s}

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3 years ago
What is the magnetic force on a proton that is moving at 4.5 x 10^7 m/s to the right through a magnetic field that is 1.6 T and
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The magnetic force on a charged particle is given as: F = qvBsinФ
B is the magnetic field.
q is the charge on the particle.
v is the velocity of the charged particle.
 Ф is the angle between magnetic field (B) & the velocity of charge (v).


⇒ F = qvb sin Ф

Here, Ф = 90 degree.
and sin 90 = 1
Putting the values in the equation, we get,

F = 1.6 x 10^-19 C × 4.5 × 10^7 m/s × 1.6 T
= 11.52 × 10^-12N
= 1.2 x 10^-11 N up
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The Environmental Protection Agency has ben concerned about the levels of radon gas in homes. If a sample of gas taken from a ba
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A small object with mass m, charge q, and initial speed v0 = 5.00 * 103 m>s is projected into a uniform electric field betwee
kotykmax [81]

Answer:

q/m = 2177.4 C/kg

Explanation:

We are given;

Initial speed v_o = 5 × 10³ m/s = 5000 m/s

Now, time of travel in electric field is given by;

t_1 = D_1/v_o

Also, deflection down is given by;

d_1 = ½at²

Now,we know that in electric field;

F = ma = qE

Thus, a = qE/m

So;

d_1 = ½ × (qE/m) × (D_1/v_o)²

Velocity gained is;

V_y = (a × t_1) = (qE/m) × (D_1/v_o)

Now, time of flight out of field is given by;

t_2 = D_2/v_o

The deflection due to this is;

d_2 = V_y × t_2

Thus, d_2 = (qE/m) × (D_1/v_o) × (D_2/v_o)

d_2 = (qE/m) × (D_1•D_2/(v_o)²)

Total deflection down is;

d = d_1 + d_2

d = [½ × (qE/m) × (D_1/v_o)²] + [(qE/m) × (D_1•D_2/(v_o)²)]

d = (qE/m•v_o²)[½(D_1)² + D_1•D_2]

Making q/m the subject, we have;

q/m = (d•v_o²)/[E((D_1²/2) + (D_1•D_2))]

We have;

E = 800 N/C

d = 1.25 cm = 0.0125 m

D_1 = 26.0 cm = 0.26 m

D_2 = 56 cm = 0.56 m

Thus;

q/m = (0.0125 × 5000²)/[800((0.26²/2) + (0.26 × 0.56))]

q/m = 312500/143.52

q/m = 2177.4 C/kg

8 0
3 years ago
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