**Answer:**

**a.**

**b.1058 N**

**Explanation:**

We are given that

Mass of each dog,M=18.5 kg

Mass of sled with rider,m=250 kg

a.Average force,F=185 N

By Newton's second law

b.By Newton's second law

Substitute the values

Hence, the force in the coupling between the dogs and the sled=**1058 N**

**Answer:**

Frequency

**Explanation:**

The frequency ( ) of a wave is the number of waves passing a point in a certain time.

**Answer:**

It has about 11 fewer days. It does not have seasons. Its new year always occurs in February instead of on January 1.

**Explanation:**

if it moves 7m/s, that means every second it goes 7m. Now we just multiply by the time (20 seconds) and end up with **140m.**

According to Stefan-Boltzmann Law, the thermal energy radiated by a radiator per second per unit area is proportional to the fourth power of the absolute temperature. It is given by;

P/A = σ T⁴ j/m²s

Where; P is the power, A is the area in square Meters, T is temperature in kelvin and σ is the Stefan-Boltzmann constant, ( 5.67 × 10^-8 watt/m²K⁴)

Therefore;

Power/square meter = (5.67 × 10^-8) × (3000)⁴

= 4.59 × 10^6 Watts/square meter