Acheerleader lifts his 43.8 kg partner straight up off the ground a distance of 0.737 m before releasing her. assume the partner’s velocity is zero at the beginning and the end of the lift. the acceleration of gravity is 9.8 m/s 2 . if he does this 27 times, how much work has he done? answer in units of j.
the planet mars is visible without a telescope on many clear nights. the planets jupiter, mercury, venus and saturn are also viewable without the aid of magnification.
answer : lower than the mercury in the vessel, and shaped like the outside of an umbrella.
explanation : we know that the capillary action, in this the inter-molecular force within the mercury exceed those between the glass and the mercury
hence, a convex meniscus form and capillary action work in reverse.
so, if a small diameter open glass tube is partially immersed in a vessel containing mercury, the surface of the mercury inside the tube will be lower than the mercury in the vessel, and shaped like the outside of an umbrella.
the kinetic energy is 8100 j.
mass is 50.0kg and velocity is 18 m/s, the kinetic energy is:
as we know the formula of kinetic energy which is k.e = ½ ( mv ^ 2 ),
mass = m = 50.0kg
velocity = v = 18 m / s,
by putting values in the formula,
k.e = ½ ( mv ^ 2 ),
k.e = ½ ( 50kg ) . ( 18 m / s ) ^ 2
k.e = ½ ( 50kg ) . ( 324 ),
=> k.e = 1/2 ( 16200 ),
=> k.e = 16200 / 2,
=> k.e = 8100j.
hence, the kinetic energy ( k.e ) is 8100 joule ( j ).
i) you walk barefoot on the hot street and it burns your toes.
the road is in direct contact with your skin. thermal energy from the road will transfer to the bottom of your feet, then to the rest of your body. this is an example of conduction.
ii) when you get into a car with hot black leather in the middle of the summer and your skin starts to get burned.
just like in the previous example, the hot leather is in direct contact with your skin (i guess if you're going to drive naked). thermal energy from the leather will transfe to your skin, then to the rest of your body. this is also conduction.
iii) a flame heats the air inside a hot air balloon and the balloon rises.
the flame heats air directly at the bottom of the balloon. the warm air expands and becomes less dense. this will rise and let the unheated, denser air in the balloon fall down toward the flame. this is an example of the convection cycle.
iv) a boy sits to the side of a campfire. he is 10 feet away, but still feels warm.
the campfire heats air directly nearby. the warm air expands and moves away from the fire in all directions, leaving behind unheated, denser air to be heated up. some of the warm air reaches the boy. this is another example of convection.
the answer is a) 1 and 2.