The hard external covering of some invertebrates is called a what

A bus is moving and has 500000 joules of kinetic energy. The brakes are applied and the bus stops. How much work is needed to st

Bad White [126]

For the work-energy theorem, the work needed to stop the bus is equal to its variation of kinetic energy:
$W=K_f - K_i$
where
W is the work
Kf is the final kinetic energy of the bus
Ki is the initial kinetic energy of the bus

Since the bus comes at rest, its final kinetic energy is zero: $K_f = 0$ , so the work done by the brakes to stop the bus is
$W=-K_i = -500000 J$
And the work done is negative, because the force applied by the brake is in the opposite direction to that of the bus motion.

8 0

3 years ago

a fan is rotating clockwise and its acceleration has a positive sign. is the angular velocity of the fan speeding up, slowing do

balu736 [363]

Answer:

The angular velocity is slowing down.

Explanation:

By convention, if a rigid body is rotating clockwise, the angular velocity is negative.
If the angular acceleration has a positive sign, since the angular acceleration and the angular velocity have opposite signs, this means that the angular velocity is slowing down.

5 0

3 years ago

A gas expands against a constant external pressure of 2.00 atm until its volume has increased from 6.00 to 10.00 L. During this

mars1129 [50]

Answer:

ΔU = - 310.6 J (negative sign indicates decrease in internal energy)

W = 810.6 J

Explanation:

a.

Using first law of thermodynamics:

Q = ΔU + W

where,

Q = Heat Absorbed = 500 J

ΔU = Change in Internal Energy of Gas = ?

W = Work Done = PΔV =

P = Pressure = 2 atm = 202650 Pa

ΔV = Change in Volume = 10 L - 6 L = 4 L = 0.004 m³

Therefore,

Q = ΔU + PΔV

500 J = ΔU + (202650 Pa)(0.004 m³)

ΔU = 500 J - 810.6 J

ΔU = - 310.6 J (negative sign indicates decrease in internal energy)

b.

The work done can be simply calculated as:

W = PΔV

W = (202650 Pa)(0.004 m³)

W = 810.6 J

7 0

3 years ago

A wave has a frequency of 35 Hz and a wavelength of 15 meters, what is the speed of the wave?

Mila [183]

Answer:

f lamda = c

Explanation:

525 m/s is the speed

5 0

3 years ago

A 60kg bicyclist (including the bicycle) is pedaling to the

Fittoniya [83]

a) 4 forces

b) 186 N

c) 246 N

Explanation:

a)

Let's count the forces acting on the bicylist:

1) Weight ( $W=mg$ ): this is the gravitational force exerted on the bicyclist by the Earth, which pulls the bicyclist towards the Earth's centre; so, this force acts downward (m = mass of the bicyclist, g = acceleration due to gravity)

2) Normal reaction (N): this is the reaction force exerted by the road on the bicyclist. This force acts vertically upward, and it balances the weight, so its magnitude is equal to the weight of the bicyclist, and its direction is opposite

3) Applied force ( $F_A$ ): this is the force exerted by the bicylicist to push the bike forward. Its direction is forward

4) Air drag ( $R$ ): this is the force exerted by the air on the bicyclist and resisting the motion of the bike; its direction is opposite to the motion of the bike, so it is in the backward direction

So, we have 4 forces in total.

b)

Here we can find the net force on the bicyclist by using Newton's second law of motion, which states that the net force acting on a body is equal to the product between the mass of the body and its acceleration:

$F_{net}=ma$