18. How would you respond if you suddenly touched a sharp thorn while picking a flower? Describe the reflex action that occurs during the process and represent it as a well-labeled diagram.

19. The mass of a car along with its rider is 1000 kg. It is moving with a velocity of 72 km/h and takes 5 seconds to stop after the brakes are applied. Calculate the force exerted by the brakes.

In physics, stopping distances and times for cars with different masses but the same kinetic energy can be explained by considering inertia and force. Work being done can be classified as positive, negative, or zero under different scenarios.

Explanation:

Stopping Distances: When two cars with different masses but the same kinetic energy use the same force to stop, the one with the greater mass will have a longer stopping distance due to inertia.

Time to Stop: The time required for the car to stop is longer for the heavier car as it takes more time to decelerate due to its greater mass.

Work Being Done: (a) Positive - as the bull is displacing the ground, (b) Positive - work is being done to pull the net, (c) Negative - resisting the motion, (d) Zero - no displacement in the vertical direction.

Learn more about Kinetic Energy and Work here:

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