Answer:
Gravity
Explanation:
It is gravity because the sun's gravity pulls all the planets towards itself and keeps the planets in the sun's orbit
Answer:
1 second
Explanation:
The impulse exerted on the boy is equal to its change of momentum:

where
F = 500 N is the push on the boy
is the contact time
m = 25 kg is the mass of the boy
is the change in velocity of the boy
Solving the formula for the contact time, we find

As the centripetal force<span> acts upon an </span>object moving <span>in a </span>circle<span> at constant speed, the </span>force<span> always acts inward as the velocity of the </span>object<span> is directed tangent to the </span>circle. ... In fact, whenever the unbalanced centripetal force<span> acts perpendicular to the direction of </span>motion<span>, the speed of the </span>object will<span> remain constant.</span>
Answer:
The runner's acceleration was 
Explanation:
<u>Constant Acceleration Motion</u>
It's a type of motion in which the velocity of an object changes by an equal amount in every equal period of time.
Being a the constant acceleration, vo the initial speed, vf the final speed, and t the time, the following relation applies:

Solving for a:

The runner speeds up from vo=5 m/s to vf=9 m/s in t=4 seconds, thus:


The runner's acceleration was 
In order to find the efficiency first we will find the Change in Potential energy of the small stone that robot picked up
First we will find the mass of the stone
As it is given that stone is spherical in shape so first we will find its volume



Now it is given that it's specific gravity is 10.8
So density of rock is

mass of the stone will be



now change in potential energy is given as

here
g = gravity on planet = 0.278 m/s^2
H = height lifted upwards = 15 cm


Now energy supplied by internal circuit of robot is given by

V = voltage supplied = 10 V
i = current = 1.83 mA
t = time = 12 s


Now efficiency is defined as the ratio of output work with given amount of energy used


so efficiency will be 23 %