Question

Trump slides his shoe off the edge of a table at point A with an initial velocity of 30 m/s and experiences no air resistance. The height of the tabletop above the ground is 0.75 m.

(a) What is the speed (not the velocity) of the puck just before it touches the ground?

(b) What is the distance between point A and the point where the puck hits the ground?

c) What is the angle below the horizontal of the velocity of the puck just before it hits the ground?

d) Provide a final drawing with all the vectors

Answer 1

A)

Here,the puck executes a projectile motion,projected horizontally with initial velocity is in the horizontal direction.

Given that there is no air resistances,

Also,since there is no acceleration in horizontal direction,the horizontal velocity remains the same equal,

But there is an acceleration of in the downward direction for the vertical motion.

Alos,the initial vertical velocity=0m/s

Consider the vertical motion of the puck,

initial vertical velocity,

Hieght or displacement,

Acceleration,

FInal vertical velocity,

From the Newtons 3rd equation of motion,

Also the final horizontal velocity when it touches the ground,

So,the magnitude resultant velocity or speed  just before it touches ground,

So,the speed of the puck just before it touches the ground,

B)

Here consider the vertical motion,

Let the time taken to hit the puck at the ground be,

From Newtons 1st equation of motion,

So,tme taken,

Now consider the horizontal motion,Here since there is no acceleration on the puck in horizontal direction,so the horizontal velocity remains constant.

ie,

So,the horizontal distance travelled before it hits ground,

Or,

C)

We have just before it touches ground,it has a final vertical velocity in vertically downward direction,ie,

Also the puck has a horizontal velocity just before it hits ground,

So,the angle made by resultant final velocity just before it touches ground,

We have,

So,

So,the angle below horizontal of velocity of puck just before it touches ground,

D)