There are different types of contact forces like normal Force, spring force, applied force and tension force.
Answer:
a switch that flicks the light on
Answer: 
Explanation:
Combined gas law is the combination of Boyle's law, Charles's law and Gay-Lussac's law.
The combined gas equation is,
where,
= initial pressure of gas at STP = 1 atm
= final pressure of gas = 2.67 atm
= initial volume of gas =
= final volume of gas = ?
= initial temperature of gas at STP =
= final temperature of gas =
Now put all the given values in the above equation, we get:

Thus the final volume will be 
Net force acting on mass = 20 - 15 = 5N. ( subtracted cuz friction always opposes the motion i.e it always acts in direction opposite to the motion of the object). According to Newton's 2nd law of motion, F(net) = ma. a =F (net) / m = 5/10 = 0.5 m/s^2. Hope it helps :)