Mrs. Wilson is driving her car to the store. She drives on a street where the speed limit is 50 mph. Then she turns onto a street where the speed limit is 45 mph. What happens to the kinetic energy of her car?
a
When she slows from 45 mph to 50 mph, the car’s kinetic energy decreases.
b
When she slows from 50 mph to 45 mph, the car’s kinetic energy increases.
c
When she speeds up from 45 mph to 50 mph, the car’s kinetic energy is changed to potential energy.
d
When she slows from 50 mph to 45 mph, the car’s kinetic energy stays the same.
d. When Mrs. Wilson slows down from 50 mph to 45 mph, the car’s kinetic energy stays the same. Kinetic energy is directly proportional to the square of the velocity. Therefore, as the speed decreases, the kinetic energy also decreases, and vice versa. However, in this case, the car is only slowing down by 5 mph, which is not a significant enough change to affect the car's kinetic energy noticeably.
d
When Mrs. Wilson slows down from 50 mph to 45 mph, the car's kinetic energy stays the same. This is because the kinetic energy of an object depends on both its mass and its speed. Since only the speed is changing, and not the mass of the car, the kinetic energy remains constant. It's like when you slow down while eating a burger, the energy you get from the burger doesn't change, it's just your enthusiasm that decreases!
d
When she slows from 50 mph to 45 mph, the car's kinetic energy stays the same.
To answer this question, we need to understand the relationship between speed and kinetic energy.
The formula for kinetic energy is:
Kinetic energy = 0.5 * mass * velocity^2
Given that Mrs. Wilson's car is already in motion, we can assume that the mass of the car remains constant. Therefore, we can focus on the change in velocity (speed).
When Mrs. Wilson slows down from 50 mph to 45 mph, her car's velocity decreases. According to the formula, if velocity decreases, the kinetic energy will also decrease.
Therefore, the correct answer is:
a) When she slows from 45 mph to 50 mph, the car’s kinetic energy decreases.