A 200-g hockey puck is launched at an initial speed of 16 m/s up a metal ramp that is inclined at a 30° angle. The coefficients of static and kinetic friction between the hockey puck and the metal ramp are µs = 0.40 and µk = 0.30, respectively. What vertical height does the puck reach above its starting point

Respuesta :

Answer:

h = 8.588 m

Explanation:

Given:

Mass of hockey puck:  m  =  200  g  =  0.2  K g

Angle of incline:  θ  =  30º   (with respect to horizontal)

Coefficient of static and kinetic friction between the puck and ramp:  

μ s  =  0.4   and    μk  =  0.3

initial speed:  

v  =  3.5  m /s

Let  h  be the vertical height reached by the puck, above the ground. This corresponds to a distance of  

d =  h *sin  30º =  2 *h

along the incline. As the puck is moving, only kinetic friction comes into play as it climbs up the incline. Let  N  be the normal reaction exerted by the metal ramp on the ball. Then,

N  =  m*g *cos  θ  =  0.2 *9.8 1*cos  30 º =  1.6991  N

Therefore, kinetic friction acting on the puck is:  

F k  =  μ k *N  =  0.3 *1.6974  =  0.50974 N

From work energy theorem, the change in kinetic energy should equal the work done by friction and gravity. Therefore,

0.5*  0.2 *16²  =  0.50974 *2h + 0.2*9.81*h

⇒  h = 8.588 m

The vertical height that the puck reach above its starting point is

16.847 m

Given

U = 16 m/s

m = 200 g

θ = 30°

µs = 0.40

µk = 0.30

the puck was moving at a initial velocity u due to friction and gravitational force the puck will stop at a point the height at this point is what we are looking for. from Newtons law of motion

[tex]v^{2} = u^{2} +2as[/tex]

v is final velocity which should be zero

u is initial velocity

a is negative acceleration

s is distance which is the required height

0 = [tex]u^{2} + 2as[/tex]

s = [tex]\frac{- (u^{2} )}{2a}[/tex]

to find the acceleration (deceleration) we resolve the forces as follows

sum of vertical forces is zero

N is Normal reaction

g is acceleration due to gravity = 10

N = m g cos θ

considering friction

vertical force Fv = N µk = m g cos θ µk

Sum of horizontal forces Fh = m a

m a = -(m g sin θ) - (m g cos θ) µk

a =  - g (sin θ + cos θ µk)

a = - (10 (sin 30 + cos 30 * 0.3))

a = - 7.598 m/[tex]s^{2}[/tex]

solving for s gives

s = [tex]\frac{- (u^{2} )}{-2a}[/tex]

[tex]s = \frac{16^{2} } {2*7.598}[/tex]

[tex]s = 16.847 m[/tex]

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