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.)

A. Mary's snowball has a greater downward acceleration than Debra's snowball.
B. Debra's snowball has exactly the same acceleration as Mary's snowball.
C. Debra's snowball will stay in the air longer than Mary's snowball.
D. Mary's snowball will stay in the air longer than Debra's snowball.
E. Both snowballs will take the same amount of time to hit the ground.

Answer 1

Answer:B,C

Explanation:

Given

Mary throw her snowball $30^{\circ}$ below the horizontal

and Debra throw it at angle of $30^{\circ}$ above the horizontal

acceleration due to gravity is same in both case thus both reach the ground with same acceleration

Debra Snowball will take longer because first it completes the projectile motion to make its vertical displacement zero w.r.t  roof and then it starts moving below the roof while Mary snowball starts moving downward at the instant it is thrown.

Answer 2

Answer:B,C

Explanation:

Given

Mary throw her snowball  below the horizontal

and Debra throw it at angle of  above the horizontal

acceleration due to gravity is same in both case thus both reach the ground with same acceleration

Debra Snowball will take longer because first it completes the projectile motion to make its vertical displacement zero w.r.t  roof and then it starts moving below the roof while Mary snowball starts moving downward at the instant it is thrown.