Marcia uses a bow to shoot an arrow with initial velocity of magnitude v0 and at an angle θ above the horizontal. When the arrow returns to the same height from which it started,
A) the speed of the arrow is twice v0.
B) the speed of the arrow is 9.8 times larger than v0.
C) the speed of the arrow is again v0.
D) the speed of the arrow is sqrt(2)v0.
E) the speed of the arrow is v0/sqrt(2) .
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°. When the snowballs reach the ground below,
A) Debra’s snowball will have a higher speed than Mary’s.
B) Mary’s snowball will have a higher speed than Debra’s.
C) Both snowballs will hit the ground with the same speed.
D) Debra’s snowball never hits the ground since it is thrown upwards.
E) Mary’s snowball never hits the ground since it is thrown downwards.
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°. When the snowballs reach the ground below,
A) Debra’s snowball will stay in the air longer than Mary’s.
B) Mary’s snowball will stay in the air longer than Debra’s.
C) Both snowballs will take the same amount of time to hit the ground.
D) Debra’s snowball never hits the ground since it is thrown upwards.
E) Mary’s snowball never hits the ground since it is thrown downwards.
A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the velocity of the rock right before it hits the ground?
A) It is equal to its initial vertical velocity.
B) It is equal to its initial horizontal velocity.
C) It is equal to the magnitude of its initial velocity.
D) 0
E) Cannot be determined without additional information.
EXPERT ANSWER
Marcia uses a bow to shoot an arrow with initial velocity of magnitude v0 and at an angle θ above the horizontal. When the arrow returns to the same height from which it started,
A) the speed of the arrow is twice v0.
B) the speed of the arrow is 9.8 times larger than v0.
C) the speed of the arrow is again v0.
D) the speed of the arrow is sqrt(2)v0.
E) the speed of the arrow is v0/sqrt(2) .
Answer :C) the speed of the arrow is again v0.
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°. When the snowballs reach the ground below,
A) Debra’s snowball will have a higher speed than Mary’s.
B) Mary’s snowball will have a higher speed than Debra’s.
C) Both snowballs will hit the ground with the same speed.
D) Debra’s snowball never hits the ground since it is thrown upwards.
E) Mary’s snowball never hits the ground since it is thrown downwards.
Answer :C) Both snowballs will hit the ground with the same speed.
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°. When the snowballs reach the ground below,
A) Debra’s snowball will stay in the air longer than Mary’s.
B) Mary’s snowball will stay in the air longer than Debra’s.
C) Both snowballs will take the same amount of time to hit the ground.
D) Debra’s snowball never hits the ground since it is thrown upwards.
E) Mary’s snowball never hits the ground since it is thrown downwards.
Answer :A) Debra’s snowball will stay in the air longer than Mary’s.
A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the velocity of the rock right before it hits the ground?
A) It is equal to its initial vertical velocity.
B) It is equal to its initial horizontal velocity.
C) It is equal to the magnitude of its initial velocity.
D) 0
E) Cannot be determined without additional information.
Answer : C) It is equal to the magnitude of its initial velocity.