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2 years ago

Friction and normal force are examples of

Physics

1 answer:

siniylev [52]2 years ago

3 0

Answer:

Friction is a force that tends to oppose the relative motion between two bodies in contact. Frictional force always acts on a moving body from the direction opposite to the direction of motion. It opposes the motion, and therefore, helps to reduce the speed of the moving object. It is a contact force.

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A woman (mass= 50.5 kg) jumps off of the ground, and comes back down to the ground at a velocity of -8.4 m/s.

Blizzard [7]

Answer:

Approximately $1.6\times 10^{3}\; \rm N$ .

Explanation:

By the Impulse-Momentum Theorem, the change in this woman's momentum will be equal to the impulse that is applied to her.

The momentum $p$ of an object is equal to the product of its mass $m$ and velocity $v$ . That is: $p = m \cdot v$ .

Let $v(\text{before})$ and $v(\text{after})$ represent the velocity of the woman before and after the landing. Let $m$ represent the woman's mass.

The woman's momentum before the landing would be $m \cdot v(\text{before})$ .
The woman's momentum after the landing would be $m \cdot v(\text{after})$ .

Therefore, the change in this woman's momentum would be:

$\begin{aligned}& \Delta p \\ & = p(\text{after}) - p(\text{before}) \\ &= m \cdot (v(\text{after})- v(\text{before}))\end{aligned}$ .

On the other hand, impulse is equal to force multiplied by the duration of the force. Let $F$ represent the average force on the woman. The impulse on her during the landing would be $F \cdot t$ .

Apply the Impulse-Momentum Theorem.

Impulse: $F\cdot t$ .
Change in momentum: $m \cdot (v(\text{after})- v(\text{before}))$ .

Impulse is equal to the change in momentum:

$F \cdot t = m \cdot (v(\text{after})- v(\text{before}))$ .

After landing, the woman comes to a stop. Her velocity would become zero. Therefore, $v(\text{after}) = 0\; \rm m \cdot s^{-1}$ .

$\begin{aligned}F &= \displaystyle \frac{m \cdot (v(\text{after})- v(\text{before}))}{t} \\ &= \frac{50.5\; \text{kg} \times \left(0 \; \mathrm{m \cdot s^{-1}}- 8.4\; \mathrm{m \cdot s^{-1}}\right)}{0.27\; \rm s} \\ &\approx 1.6 \times 10^{3}\; \rm N\end{aligned}$ .

3 0

4 years ago

Why not two magnetic field lines can intersect? why not it is possible?

11111nata11111 [884]

At each point on a 'line', the direction of the 'line' is the direction of the force
on a small test magnet placed in the field at that point.

If two 'lines' crossed at the same point, that means a small test magnet placed
at that point in the field would feel a force in two different directions.

But even if that were true, then the net effect on the small test magnet would be
the vector sum of the two forces, and they would be represented by a single net
force anyway, and therefore by a single field 'line' at that point.

4 0

4 years ago

The cheetah is one of the fastest accelerating animals, for it can go from rest to 28.0 m/s in 5.20 s. If its mass is 100 kg, de

Setler79 [48]

Answer:

a)15077 W

b)20.2185 horse power

Explanation:

P=F*V

F=ma

a=Vf-VS/t

Vf=28m/s