In terms of saving energy, bicycling and walking are far more efficient means of transportation than is travel by automobile. for example, when riding at 14.5 mi/h, a cyclist uses food energy at a rate of about 400 kcal/h above what he would use if he were merely sitting still. (in exercise physiology, power is often measured in kcal/h rather than in watts. here, 1 kcal = 1 nutritionist's calorie = 4,186 j.) walking at 2.89 mi/h requires about 220 kcal/h. it is interesting to compare these values with the energy consumption required for travel by car. gasoline yields about 1.30 ✕ 108 j/gal. find the fuel economy in equivalent miles per gallon for a person bicycling.

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the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

increase masses, decrease separation

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m