Answer:
482.4 kg
Explanation:
104 calorie = 435344 J
The 2.5% of this energy equals to
435344 * 0.0025 = 10883.6 J
If this energy is converted to work done on lifting a barbell by a distance of 2.3. By the formula of Work W = force * distance then the force he exerts on the barbell is

Assuming gravitational constant g = 9.81 m/s2 then the mass of the barbell is
m = 4732 / 9.81 = 482.4 kg
Such system is called RADAR (<span>RAdio </span>Detection<span> And Ranging).
The Radar emits radio waves, that are reflected back by the object. Since the speed of the radio waves is known (their speed is equal to the speed of light), by measuring the time the waves take to come back to the source it is possible to infer the distance they covered, and so the distance of the object.</span>
Force and distance is the main criteria for the movement of the object. The work of the object can be defined as the ‘product’ of the force and distance.
Answer:
Zero
Explanation:
Average velocity is given by:

where
d is the displacement of the trip
t is the time it takes for the trip to complete
In this problem, the net displacement of the swimmer is zero. In fact:
- First, he swims 30.0 m in the north direction
- Then, he travels back (-30.0 m) in the south direction, to the starting position
Since the final position is equal to the starting position, the displacement is zero:
d = 0
And therefore, the average velocity is also zero.