In a room where g=9.81 m/s 2 , a hockey puck slides off the edge of a platform w
ID: 1331622 • Letter: I
Question
In a room where g=9.81 m/s2, a hockey puck slides off the edge of a platform with an initial velocity of 28.0m/s horizontally. The height of the platform above the ground is 2.00m. What is the speed of the puck just before it hits the ground? The air resistance is negligibly small.
A. 28m/s, B. 26.3m/s, C. 28.7m/s, D. 6.26m/s, E. 48.2m/s
A boy kicks a football with an initial velocity of 20m/s at an angle 25° above the horizontal. If we neglect air resistance, the magnitude of the acceleration of the ball while it is in flight is
A. 25m/s^2, B. 0m/s^2, C. 9.8M/s^2, D. 8.5m/s^2, E. 18m/s^2
True/False. The magnitude of a vector is only zero if all of its components are zero.
Two boxes are connect to each other by a string. The 10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension T in the string?
A. T=30N, B. T=20N, C. T<30N, D. T=10N, E. T>30 N
Explanation / Answer
Here ,
initial velocity , u = 28 m/s
height , h = 2 m
let the speed before hitting ground is v
Using third equation of motion
v^2 - u^2 = 2 * a * d
v^2 - 28^2 = 2 * 9.81 * 2
v = 28.7 m/s
the speed of puck is C) 28.7 m/s
b)
as the fottball is in freefall in the air
the magnitude of acceleration of the ball while in flight is C) 9.8 m/s^2
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