1. In moving an object of mass 10 kg through a distance of 8.0 m, 40 J of work is done. The average force exerted is?
2. What is the kinetic energy of a 20 kg object moving at a speed of 10 m/s?
3. the gravitational potential energy of a bird of mass 2.0 kg on a tree branch of height 15 m is most nearly
4. Two objects have the same mass. One is travelling twice as fast as the other. The work that must be done to stop the faster object compared to the work required to stop the slower object is:
a)two times greater
b)the same
c)four times greater
d)half as great
e)one quarter as great
5. When a rock is thrown straight up in the air, after it leaves the hand, the rock begins to slow down. This occurs because:
a) the rock is gaining potential energy as it rises and thus it must lose kinetic energy
b)the force of gravity acting on the rock increases as the rock rises
c)the forces acting on the rock are balanced
d)the potential energy of the rock decreases as the rock rises
work = force * distance
Kinetic energy = (1/2) m v^2
What on earth are you asking for? Please read your text and post your attempts to do the problems.
1. To find the average force exerted, we can use the formula for work: Work = Force x Distance. Rearranging the formula, we have Force = Work / Distance. Plugging in the values given, we have Force = 40 J / 8.0 m = 5 N. Therefore, the average force exerted is 5 Newtons.
2. The formula for kinetic energy is KE = 1/2 x mass x velocity^2. Plugging in the given values, we have KE = 1/2 x 20 kg x (10 m/s)^2 = 1000 J. Therefore, the kinetic energy of the object is 1000 Joules.
3. The formula for gravitational potential energy is PE = mass x gravity x height. Plugging in the given values, we have PE = 2.0 kg x 9.8 m/s^2 x 15 m = 294 J. Therefore, the gravitational potential energy of the bird is most nearly 294 Joules.
4. The work required to stop an object depends on its initial kinetic energy. Since kinetic energy is directly proportional to the square of velocity (KE = 1/2 x mass x velocity^2), the work required to stop the faster object would be greater than the work required to stop the slower object.
We can calculate the ratio of the work required for the faster object to the slower object. Let's call the ratio R. Since the faster object is traveling twice as fast as the slower object, its kinetic energy is four times greater (2^2 = 4). Therefore, the work required to stop the faster object would be four times greater than the work required to stop the slower object, resulting in ratio R = 4.
Hence, the correct answer is (c) four times greater.
5. The correct answer is (a) the rock is gaining potential energy as it rises and thus it must lose kinetic energy. When the rock is thrown straight up, it first has a high initial velocity, resulting in high kinetic energy. As it rises, it gains height and potential energy due to the work done against gravity. Therefore, its kinetic energy decreases as it converts into potential energy. The rock eventually stops rising and starts falling back down due to the gravitational force pulling it back.