During a family car trip, a family travels for 1 hour at 70 miles per hour. Then the family travels for 2 more hours at 55 miles per hour. What is the family's average speed during the trip? A. 58.5 mph
B. 65 mph
C. 62.5 mph
D. 60 mph

Complete Question

The complete question is shown on the first uploaded image

The force on the lid when the air inside the cooker had been heated to 120°C is =  

The force on the lid when the air inside the cooker had been heated to 20°C is =

The

Explanation:

The main concept used to solve this problem is Pressure-Temperature Law.

Initially, find the pressure inside the pressure cooker by using the Pressure-Temperature Law. Then, find the force exerted by the air inside cooker on the lid of the cooker.

Fundamentals :

The Pressure-Temperature Law states that the pressure of the of a given gas held at constant volume is directly proportional to the Kelvin temperature. The increase in pressure results in an increase in the temperature and vice-versa.

The expression of the Pressure-Temperature Law is as follows:

Here, and

are the initial and final pressures and and

are the initial and final temperatures respectively.

The force in terms of pressure can be given by the following expression.  

F=(ΔP) A

Here, A is the area on which the pressure is applied and ΔP is the change in pressure

The step- step calculation is shown on the second,third,fourth, fifth image

Note: is the pressure of atmosphere