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?
my answer: 320N
2. What is the kinetic energy of a 20 kg object moving at a speed of 10 m/s?
my answer: 1000J
3. the gravitational potential energy of a bird of mass 2.0 kg on a tree branch of height 15 m is most nearly
my answer: 300J
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
my answer: a
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
my answer: d
ed by Lisa on Sunday, February 23, 2014 at 6:39pm.
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?
my answer: 320N Hmmm. force*distance=work
force=work/distance=40/8 N
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
my answer: a ***Hmmm. how does KE figure into this?
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
my answer: d ****Hmmm. Isn't PE greatest at the maximum height?
1. To find the average force exerted, we can use the formula: Work = Force x Distance. Rearranging the formula, we have Force = Work / Distance. Substituting the given values, we get Force = 40 J / 8.0 m = 5 N. Therefore, the average force exerted is 5 N.
2. The kinetic energy of an object can be calculated using the formula: Kinetic Energy = (1/2) x mass x velocity^2. Substituting the given values, we get Kinetic Energy = (1/2) x 20 kg x (10 m/s)^2 = 1000 J. Therefore, the kinetic energy of the object is 1000 J.
3. The gravitational potential energy can be calculated using the formula: Gravitational Potential Energy = mass x gravity x height. Substituting the given values, we get Gravitational Potential Energy = 2.0 kg x 9.8 m/s^2 x 15 m = 294 J. Therefore, the gravitational potential energy of the bird on the tree branch is most nearly 294 J.
4. The work done to stop an object is equal to the change in kinetic energy. Since both objects have the same mass, their change in kinetic energy will be directly proportional to their square of velocity. The formula for kinetic energy is KE = (1/2) x mass x velocity^2. As the faster object is traveling twice as fast, its kinetic energy is (1/2) x mass x (2v)^2 = 4 x (1/2) x mass x v^2. Therefore, the work required to stop the faster object compared to the slower object is four times greater. Hence, the correct answer is c) four times greater.
5. When a rock is thrown straight up in the air, it begins to slow down due to the force of gravity. As the rock rises, it gains potential energy and loses kinetic energy, as indicated by option a). The potential energy of an object increases as it rises, which means the kinetic energy must decrease. Therefore, the correct answer is a) the rock is gaining potential energy as it rises and thus it must lose kinetic energy.
1. To find the average force exerted, you can use the equation for work:
Work = force x distance
Given the work done (40 J) and the distance (8.0 m), you can rearrange the equation to solve for force:
force = work / distance
Substituting the values, you get:
force = 40 J / 8.0 m = 5 N
So, the average force exerted is 5 N.
2. The kinetic energy of an object can be calculated using the formula:
Kinetic energy = (1/2) x mass x velocity^2
Given the mass (20 kg) and the velocity (10 m/s), you can substitute the values into the formula:
Kinetic energy = (1/2) x 20 kg x (10 m/s)^2 = 1000 J
Therefore, the kinetic energy of the object is 1000 J.
3. The gravitational potential energy of an object can be calculated using the formula:
Gravitational potential energy = mass x acceleration due to gravity x height
Given the mass (2.0 kg), the acceleration due to gravity (9.8 m/s^2), and the height (15 m), you can substitute the values into the formula:
Gravitational potential energy = 2.0 kg x 9.8 m/s^2 x 15 m = 294 J
So, the gravitational potential energy of the bird on the tree branch is approximately 294 J.
4. The work done to stop an object is given by the equation:
Work = (1/2) x mass x velocity^2
Since both objects have the same mass, the work required to stop them depends on the velocity. The work required is directly proportional to the square of the velocity.
Therefore, if one object is traveling twice as fast as the other, the work required to stop it would be four times greater.
Hence, the correct answer is c) four times greater.
5. When a rock is thrown straight up in the air, it experiences a decrease in velocity as it rises due to the force of gravity acting upon it.
The correct answer is a) the rock is gaining potential energy as it rises and thus it must lose kinetic energy. As the rock rises, its kinetic energy decreases and is converted into potential energy. This is due to the change in the object's height or position in the gravitational field. Gravity pulls the rock downwards, slowing it down until it reaches its maximum height, at which point its upward velocity becomes zero.