1 kilometer= 1000 meters
6.8 kilometers= 6800 meters
The answer is d. i hope this helps :D
Answer:
The correct options are;
a. <u>ii. Savery engine</u> The boiler could not withstand the steam pressure needed to lift water beyond 6 m.
b. <u>i.Gunpowder engine </u> The engine had no mechanism to move the piston back to complete a cycle
c. <u>iii. Newcomen engine</u> The continual reheating needed after each cooling of the engine cylinder required tremendous amount of thermal energy
d. <u>iv. Watt engine</u> This engine was large and massive and less efficient than thought possible
Explanation:
a. The evaporation of the water due to the effect of creating a vacuum limits the Savery's engine pressure differential to about 20 (which is approximately 6 meters) to 25 feet of suction
b. In The gunpowder engine after providing power to a mass, there is less provision to move the piston to a position to lift another mass
c. Energy from burning of fuel was needed to heat the steam cylinder (the steam and the steel wall) repeatedly which consumed a considerable energy in the Newcomen engine
d. In the Watt steam engine the increased efficiency attainable was 17.4% while the actual efficiency was about 11% with the addition of a separate condenser unit.
1) Answer D not at all
The car is not experiencing any frictional force so that implies that there is no force acting on the car once it starts motion. So, according law of inertia, the car will continue to move and no other force is required.
Friction force is the resistance force that opposes the motion of any object. It arises due to the contact of surfaces.
2) Answer C none
There is no force on any spaceship moving far from any planet. So, according to law of inertia the spacecraft will continue to move at same speed.
Law of inertia states that any object keeps in the state of motion or rest unless a non zero external force is applied on it.