Question

A free-wheeling motor cyclist of mass (including her machine) 100kg is pushed from rest over a distance of 10m. If the push of 250N acts against a frictional force of 70N, calculate her kinetic energy and velocity when the push ends

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Answer 1

To calculate the kinetic energy and velocity when the push ends, we can find the net force acting on the motorcyclist, calculate the acceleration, and use the equation of motion and kinetic energy formula.

Step-by-step explanation:

To calculate the kinetic energy and velocity when the push ends, we can start by finding the net force acting on the motorcyclist. The net force can be calculated by subtracting the frictional force from the push force:

Net force = Push force - Frictional force
Net force = 250 N - 70 N
Net force = 180 N

Next, we can calculate the acceleration of the motorcyclist using Newton's second law:

Acceleration = Net force / Mass
Acceleration = 180 N / 100 kg
Acceleration = 1.8 m/s²

Using the equation of motion, we can find the final velocity when the push ends:

Final velocity = Initial velocity + (Acceleration x Distance)
Final velocity = 0 + (1.8 m/s² x 10 m)
Final velocity = 18 m/s

Finally, we can calculate the kinetic energy using the formula:

Kinetic energy = 0.5 x Mass x (Velocity)²
Kinetic energy = 0.5 x 100 kg x (18 m/s)²
Kinetic energy = 16200 J