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Irina18 [472]
3 years ago
13

A baseball of mass m1 = 0.45 kg is thrown at a concrete block m2 = 7.25 kg. The block has a coefficient of static friction of μs

= 0.74 between it and the floor. The ball is in contact with the block for t = 0.185 s while it collides elastically.
a. Write an expression for the minimum velocity the ball must have, vmin, to make the block move.
b. What is the velocity in m/s?
Physics
1 answer:
miskamm [114]3 years ago
8 0

Answer:

a. v = \frac{mu_sm_2g\Delta t}{m_1}

b. 21.64 m/s

Explanation:

Let g = 9.81m/s2

a. The weight of the block is product of its mass and gravitational acceleration

W = m_2g = 7.25*9.81 = 71.1225N

which is also the normal force acting on the block from the floor so it stays balanced.

N = 71.225N

The static friction of the block is product of its normal force from the floor and the friction coefficient

F_s = \mu_sN = \mu_sW = mu_sm_2g

For the block to move, the force generated by the impact must be at least equal to the static friction.

F = F_s = mu_sm_2g

The impulse is product of this force and time duration of impact.

I = F\Delta t = mu_sm_2g\Delta t

As impulse is generated by change in momentum of the ball, which is product of its mass and velocity v

I = \Delta p = m_1\Delta v

mu_sm_2g\Delta t = m_1 v

v = \frac{mu_sm_2g\Delta t}{m_1}

b. v = \frac{mu_sm_2g\Delta t}{m_1} = \frac{0.74*7.25*9.81*0.185}{0.45} = 21.64 m/s

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