Physics Chapter 10 Energy, Work, And Simple Machines

Explanation
The mechanical advantage of a pulley system is calculated by dividing the load force by the effort force. In this case, the load force is 300 N and the effort force is 100 N. Therefore, the mechanical advantage is 300/100 = 3.

Explanation
The work done on an object is calculated by multiplying the force applied to the object by the distance over which the force is applied. In this case, the force applied is 100 N and the distance is the height of the ramp, which is 3.0 m. Therefore, the work done on the box is 100 N * 3.0 m = 300 J. However, since the force is being applied in the opposite direction of the displacement (up the ramp), the work done is negative. Therefore, the correct answer is -300 J.

Explanation
The overall efficiency of the compound machine can be calculated by multiplying the efficiencies of the ramp and the pulley. The efficiency of the ramp is 50% and the efficiency of the pulley is 90%. Multiplying these two efficiencies together gives us an overall efficiency of 45%.

Explanation
When the friend exerts a force opposite to the skater's movement, it acts as a negative force or an opposing force. This force causes the skater to decelerate, reducing his speed from 2.0 m/s to 1.0 m/s. The change in kinetic energy can be calculated using the formula ΔKE = 0.5 * m * (vf^2 - vi^2), where m is the mass and vf and vi are the final and initial velocities, respectively. Plugging in the values, we get ΔKE = 0.5 * 50 kg * ((1.0 m/s)^2 - (2.0 m/s)^2) = 0.5 * 50 kg * (-3 m^2/s^2) = -75 J. Since the change in kinetic energy is negative, we take the absolute value to get 75 J.

Explanation
The pulley system's ideal mechanical advantage can be calculated by dividing the distance the rope is pulled (2.0 m) by the distance the block is raised (0.40 m). This calculation gives a result of 5.0, which represents the pulley system's ideal mechanical advantage.

Explanation
The power used to carry an object up a ramp is given by the equation P = W/t, where P is power, W is work, and t is time. Since both people are carrying identical boxes up the ramp, the work done by each person is the same. However, the time taken by one person is half of the time taken by the other person. Therefore, the person who takes 2.0s to walk up the ramp will have a power of 20W (40N/2.0s = 20W), while the person who takes 4.0s will have a power of 10W (40N/4.0s = 10W). The difference in power between the two people is 20W - 10W = 10W.

Explanation
The work done on an object can be calculated by multiplying the force applied to the object by the distance it moves in the direction of the force. In this case, the force applied by the player's foot is 5N and the distance the ball rolls is 10m. Therefore, the work done on the ball is 5N * 10m = 50J.

The kinetic energy gained by the ball is equal to the work done on it. Therefore, the ball gains 50J of kinetic energy.

Since the question asks for the amount of kinetic energy gained from the player, the correct answer is 0.5J.

Explanation
use e = Wo/Wi x 100

Explanation
use W = Fd remember that the Force is that of gravity