(i) First, we need to calculate the kinetic energy of the runner. The formula for kinetic energy is KE = 1/2 * m * v^2, where m is the mass and v is the velocity. However, the velocity needs to be in m/s, not km/h. So, we convert 21 km/h to 5.83 m/s.

Plugging the values into the formula, we get KE = 1/2 * 72 kg * (5.83 m/s)^2 = 1223.38 Joules.

Since the runner started from rest, all of this kinetic energy came from work done on the runner. So, the work done is 1223.38 Joules.

(ii) Power is defined as work done per unit time. So, we divide the work done by the time it took.

Power = 1223.38 Joules / 1.8 s = 679.66 Watts.

(iii) When running at a constant speed, the runner is doing work to overcome the force of the wind. The power required is the work done per unit time, which is the force times the distance travelled per unit time (which is the speed).

However, the speed needs to be in m/s, not km/h. So, we convert 21 km/h to 5.83 m/s.

Then, we multiply the force by the speed to get the power: Power = 35 N * 5.83 m/s = 204.05 Watts.

Question

(i) First, we need to calculate the kinetic energy of the runner. The formula for kinetic energy is KE = 1/2 * m * v^2, where m is the mass and v is the velocity. However, the velocity needs to be in m/s, not km/h. So, we convert 21 km/h to 5.83 m/s.

Plugging the values into the formula, we get KE = 1/2 * 72 kg * (5.83 m/s)^2 = 1223.38 Joules.

Since the runner started from rest, all of this kinetic energy came from work done on the runner. So, the work done is 1223.38 Joules.

(ii) Power is defined as work done per unit time. So, we divide the work done by the time it took.

Power = 1223.38 Joules / 1.8 s = 679.66 Watts.

(iii) When running at a constant speed, the runner is doing work to overcome the force of the wind. The power required is the work done per unit time, which is the force times the distance travelled per unit time (which is the speed).

However, the speed needs to be in m/s, not km/h. So, we convert 21 km/h to 5.83 m/s.

Then, we multiply the force by the speed to get the power: Power = 35 N * 5.83 m/s = 204.05 Watts.

Knowee AI · Accepted Answer

(i) First, we need to calculate the kinetic energy of the runner. The formula for kinetic energy is KE = 1/2 * m * v^2, where m is the mass and v is the velocity. However, the velocity needs to be in m/s, not km/h. So, we convert 21 km/h to 5.83 m/s.

Plugging the values into the formula, we get KE = 1/2 * 72 kg * (5.83 m/s)^2 = 1223.38 Joules.

Since the runner started from rest, all of this kinetic energy came from work done on the runner. So, the work done is 1223.38 Joules.

(ii) Power is defined as work done per unit time. So, we divide the work done by the time it took.

Power = 1223.38 Joules / 1.8 s = 679.66 Watts.

(iii) When running at a constant speed, the runner is doing work to overcome the force of the wind. The power required is the work done per unit time, which is the force times the distance travelled per unit time (which is the speed).

However, the speed needs to be in m/s, not km/h. So, we convert 21 km/h to 5.83 m/s.

Then, we multiply the force by the speed to get the power: Power = 35 N * 5.83 m/s = 204.05 Watts.

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