<span>Answer:
skater x km/h
cyclist 20 faster x + 20 km/h
skater 30 km
cyclist 80 km
skater time = cyclist time
t=d/r
30 / x = 80 /( x + 20
cross multiply
30 ( x + 20 ) = 80 x
30 x + 600 = 80 x
30 x - 80 x = -600
-50 x = -600
/ -50
x = 12 km/h
12 km/h skater</span>
<span>The change in internal energy is only gravitional PE because the tube is being drug up at a constant speed. Since it is at a constant speed, the change in KE is 0.
Change in PE = m*g*h = 78 kg * 10 m/s^2 * 30 m = 23400 J
Work done on the system is from the force
Work = force * distance = 350 N * 120 m = 42000 J
So, work added 42000 J to the system, but the rider's energy only increased 23400 J. Therefore, friction took up the difference. Friction is where the thermal energy comes from
Q = 42000 J - 23400 J = 18600 J.
Therfore, friction generated 18600 J of heat to the surroundings.</span>
Answer:
Explanation:
1. Frictional force is responsible for running of car and buses on roads.
2.Gravitational force exists between astronauts in space.
3. Magnetic for is responsible to attract the iron objects using a magnet
4.Electrostatic force is responsible for fiber to stick on the skin.This force occurs due to the presence of charge.
5.When a person is pushing a trolley then object experience a normal reaction from ground.
6.Gravitational force makes the planet to move in their orbits.
Answer:
as it travel through the space it behave like a wave and has an oscillating electric field components and an oscillating magnetic field