Question

Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30° above the horizontal. Which of the following statements are true about just before the snowballs reach the ground below? (There could be more than one correct choice.)

Answer 1

B) Debra's snowball will stay in the air longer than Mary's snowball.

Correct. For Debra we have a time to get up let's say
`t_1` and the same time to find the reference level and from the reference level to hit the ground let's say that takes
`t_2` so the total time to hit the ground for Debre is
`t_(Debra)= 2t_1 +t_2`

For Mary the object not need time to get up so then just take let's assume
`t_3`

But we know that
`t_(Debra)>t_(Mary)`

D) Debra's snowball has exactly the same acceleration as Mary's snowball.

True. For this case we assume that the only force acting is the grviaty and the resistence of the air can be neglected. So then the acceleration for both are the same.

Step-by-step explanation:

Assuming the following options:

A) Both snowballs will take the same amount of time to hit the ground.

False. As we can see on the figure attached, for Debra we have a time to get up let's say
`t_1` and the same time to find the reference level and from the reference level to hit the ground let's say that takes
`t_2` so the total time to hit the ground for Debre is
`t_(Debra)= 2t_1 +t_2`

For Mary the object not need time to get up so then just take let's assume
`t_3`

But we know that
`t_(Debra)>t_(Mary)`

B) Debra's snowball will stay in the air longer than Mary's snowball.

Correct. For Debra we have a time to get up let's say
`t_1` and the same time to find the reference level and from the reference level to hit the ground let's say that takes
`t_2` so the total time to hit the ground for Debre is
`t_(Debra)= 2t_1 +t_2`

For Mary the object not need time to get up so then just take let's assume
`t_3`

But we know that
`t_(Debra)>t_(Mary)`

C) Mary's snowball will stay in the air longer than Debra's snowball.

False that's totally opposed from the result that we obtain,

D) Debra's snowball has exactly the same acceleration as Mary's snowball.

True. For this case we assume that the only force acting is the grviaty and the resistence of the air can be neglected. So then the acceleration for both are the same.

E) Mary's snowball has a greater downward acceleration than Debra's snowball.

False, as we can see before the same acceleration is acting for both snowballs.