20km every 1 hr is what 20km/hr means.
so 3hrs is 20km*3=60km.
Answer:
The right sphere is negatively charged, the left sphere is charged positively.
Explanation:
When a negatively charged rod is held above the top of left sphere, the rod will attract positive charges and repel negative charges. As the sphere are initially touching each other so positive charges from the both spheres will moves toward the rod. When we separate the spheres positive charges from right sphere have already moved toward the rod i.e. left sphere, creating a deficiency of positive charges in the right sphere and excessiveness of positive charges in left sphere , hence the right sphere will remain negatively charged and left sphere will remain positively charged.
Answer:

Explanation:
m = Mass of roller coaster = 2000 kg
r = Radius of loop = 24 m
v = Velocity of roller coaster = 18 m/s
g = Acceleration due to gravity = 
Normal force at the point will be

The force exerted on the track is
.
Answer:
Heat required to raise the temperature of the aluminium is 4750 J
Explanation:
As we know that the heat energy required to raise the temperature of the aluminium is given as

here we know that
m = 50 g


so we have


Explanation:
We have,
The initial position of an object is zero.
The starting velocity is 3 m/s and the final velocity was 10 m/s.
The object moves with constant acceleration..
The area covered under the velocity-time graph gives displacement of the object. The correct option is "the area of the rectangle plus the area of the triangle under the line".