The frictional force acts upwards, so as to oppose the downward force of gravity. The reason that pressing against the wall harder makes the book stick more is because the reaction force from the wall increases and frictional force is directly proportional to reaction force.
Answer:
The answer is 0.83 seconds.
Explanation:
The formula of free fall is following:
![h=1/2*g*t^2](https://tex.z-dn.net/?f=h%3D1%2F2%2Ag%2At%5E2)
Where g=9.8 m/s^2 and t=2 seconds, the rock takes:
![h=1/2*9.8*2^2=19.6](https://tex.z-dn.net/?f=h%3D1%2F2%2A9.8%2A2%5E2%3D19.6)
19.6 meters. This is the half distance of the cliff. The whole distance is 39.2 meters. So it takes:
![39.2=1/2*9.8*t^2\\t^2=8\\t=2.83](https://tex.z-dn.net/?f=39.2%3D1%2F2%2A9.8%2At%5E2%5C%5Ct%5E2%3D8%5C%5Ct%3D2.83)
2.83 second to fall down completely. The rock takes the second half of the cliff in 0.83 seconds
Answer: Hand tools are necessary for daily activities.
Explanation:
The hand tools are useful for day to day activities they aid in pouring substances, holding things, mixing substances, cleaning and for other purposes. In a chemical laboratory the hand tools like test tube holders can help in holding the chemicals. In a medical laboratory the forceps can be useful in holding and cutting the sections without causing any harm to the hands. Hand tools avoid the direct contact with the microorganisms in medical laboratory thus protect against infections. Hand tools aid in surgical operations and they help in avoiding direct contact with the blood vessels and organs preventing contamination and infections.
Answer: ![3000\ W,\ 78,000\ J](https://tex.z-dn.net/?f=3000%5C%20W%2C%5C%2078%2C000%5C%20J)
Explanation:
Given
The voltage of the battery is ![V=12\ V](https://tex.z-dn.net/?f=V%3D12%5C%20V)
Current through the battery is ![I=250\ A](https://tex.z-dn.net/?f=I%3D250%5C%20A)
(a) Power is the product of voltage and current
Power dissipates is given by
(b) Energy delivered
![E=P\times t](https://tex.z-dn.net/?f=E%3DP%5Ctimes%20t)
![E=3000\times 26\\E=78,000\ J](https://tex.z-dn.net/?f=E%3D3000%5Ctimes%2026%5C%5CE%3D78%2C000%5C%20J)
Give me some answer choices and i will be happy to help