# Physics question

Hi, please could i have yelp on this question? The question is asking for the effect of air resistance on the time it takes for the ball to reach maximum height? Surely it would take longer for the ball to reach maximum height because air resistance slows down the object so the object will have a lower velocity?
Here is the question: https://app.gemoo.com/share/image-annotation/632433999873634304?codeId=M07pK4L6eb6WR&origin=imageurlgenerator

Thank you!!
When air resistance is taken into account, the time during which the ball rises would be longer than the time during which it falls. Air resistance acts to slow down the upward motion of the ball, therefore it takes longer to reach its highest point. Conversely air resistance also acts to speed up the downward motion of the ball, causing it to fall faster than it would in a vacuum. As a result, the time taken for the ball to rise against air resistance is longer than the time taken for it to fall.
Original post by BenzeneRing12
When air resistance is taken into account, the time during which the ball rises would be longer than the time during which it falls. Air resistance acts to slow down the upward motion of the ball, therefore it takes longer to reach its highest point. Conversely air resistance also acts to speed up the downward motion of the ball, causing it to fall faster than it would in a vacuum. As a result, the time taken for the ball to rise against air resistance is longer than the time taken for it to fall.
Thank you for your reply, but the markscheme says that the time taken to reach maximum height decreases? As you said, when the ball travels upwards air resistance opposes motion so there would be a resultant force downwards so surely it would take longer for the ball to reach maximum height? Thanks!
Could you link the full questions so I can get a better understanding of it
When going up air resistance and weight of the ball act in the same direction so the velocity decreases at a faster rate than - 9.8 m/ss.

as the ball in air is falling the acceleration due to gravity is decreasing. This is because the ball's weight and air resistance are acting in opposite directions. As the ball speeds up air resistance increases and this means that the resultant force is decreasing.
Original post by BenzeneRing12
Could you link the full questions so I can get a better understanding of it

Question 3biv
Air resistance would cause the time taken for the ball to reach maximum height to be less

The ball is moving upwards. Acceleration due to gravity is downwards. This causes the upward velocity of the ball to decreases. Now in the presence of air resistance (which opposes motion and hence is also downward), the downward acceleration is greater, causing the upward velocity to decrease.

This causes a reduction the max height achievable by the ball

At maximum height, the velocity of the ball is zero. Due to air resistance the upwards velocity decreases by a larger magnitude each second and becomes zero at a faster rate compared to if it was in a vacuum.

So when velocity is zero, maximum height is reached. Maximum height is reached in a shorter time when there is air resistance
Original post by BenzeneRing12
Air resistance would cause the time taken for the ball to reach maximum height to be less
The ball is moving upwards. Acceleration due to gravity is downwards. This causes the upward velocity of the ball to decreases. Now in the presence of air resistance (which opposes motion and hence is also downward), the downward acceleration is greater, causing the upward velocity to decrease.
This causes a reduction the max height achievable by the ball
At maximum height, the velocity of the ball is zero. Due to air resistance the upwards velocity decreases by a larger magnitude each second and becomes zero at a faster rate compared to if it was in a vacuum.
So when velocity is zero, maximum height is reached. Maximum height is reached in a shorter time when there is air resistance
Thank you, i understand most of this but i have one question, i don’t understand how if downward acceleration is greater, upward velocity decreases?
Original post by BenzeneRing12
When air resistance is taken into account, the time during which the ball rises would be longer than the time during which it falls. Air resistance acts to slow down the upward motion of the ball, therefore it takes longer to reach its highest point. Conversely air resistance also acts to speed up the downward motion of the ball, causing it to fall faster than it would in a vacuum. As a result, the time taken for the ball to rise against air resistance is longer than the time taken for it to fall.

Are you sure that air resistance acts to speed up the downward motion of ball? If that is the case, how can parachutists land safely?
If you are studying at university or A level, I recommend that you consult your lecturers or teachers.
If you are not studying at university or A level, then watch this video.
https://youtu.be/ElpqPZd1RJU?si=Qt4gQeoQRCxk60x5
Original post by anonymous294
Thank you, i understand most of this but i have one question, i don’t understand how if downward acceleration is greater, upward velocity decreases?

I think you are asking the wrong question or you are unsure of what you are asking.
When we throw an object vertically upward, the magnitude of the initial upward velocity will decrease on the way upward.
This should be a “common knowledge” or “common experience”.