A sprinter accelerates from rest to a velocity of 12m/s in the first 6 seconds of the 100 meter dash .

Answer:

The acceleration of the platform is - 1.8 m/s²

Explanation:

The net force on a body causes that body to accelerate in the direction of the resultant force applied.

Setting up the force equilibrium for the configuration:

ma = 800 - mg

100a = 800 - 100×9.8

100a = - 180

100a = - 180

a = - 1.8 m/s²

This indicates that the body is falling downward.

Answer:

The time required is 20 μs

Explanation:

Here is the data provided:

temperature = 20°C  = 293 K

radius = 1 cm

atomic mass of air = 29 u

To determine

the duration for air to refill the vacuum space

solution:

We calculate the root mean square velocity of air particles. This can be expressed as:

where m indicates mass, t is temperature, v is speed, and R is the ideal gas constant, which is approximately 8.3145 (kg·m²/s²)/K·mol.

v = ............................1

v =

Resulting in v = 501.99 m/s.

<pNow, to cover the distance of 1 cm,<pThe duration needed for air is calculated as:

time taken =

which gives us:

time taken =

so, time taken = 19.92 × seconds = 20μs.

Thus, the required time is 20 μs.

Part 1) Which metal will cool the fastest?
To determine this, we need to consider the heat flow rate formula, which indicates the speed at which a substance can gain or lose heat:

where:
denotes the heat exchanged
indicates the duration
k represents the thermal conductivity of the material
A is the area over which heat transfer takes place
shows the change in temperature
x is the thickness of the substance
It is evident that the heat flow rate is directly related to k, the thermal conductivity. Thus, a higher value of k means that the metal will cool more quickly.
Upon examining the thermal conductivity values for each metal, we observe:
- Aluminium: 237 W/(mK)
- Copper: 401 W/(mK)
- Gold: 314 W/(mK)
- Platinum: 69 W/(mK)
Consequently, copper has the highest heat flow rate, making it the metal that cools the fastest.

Part 2) Which sample of copper demonstrates the greatest increase in temperature
To address this part, we can examine how the heat exchanged Q correlates with temperature increase :

where m indicates the mass and Cs represents the specific heat capacity of the material. By rearranging the equation, we derive

As a result, it becomes clear that the temperature increase is inversely related to the mass m. Thus, the block exhibiting the highest temperature rise will be the one with the least mass, hence the right choice is A) 0.5 kg.

A bathroom scale operates under gravitational influence. Typically, a reading is captured when your body applies force onto the scale. Yet in this scenario, as both you and the scale move downwards, your body ceases to press against the scale. Consequently, the result is:

<span>The scale reading will instantly drop to zero</span>

Answer:

50 meters

Explanation: