A horse has an acceleration of 2 m/s2. If it starts from rest, how fast is it going after 1.7 seconds?
2 answers:
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(a) 12.8 kg m/s
The impulse delivered by the bat on the baseball is equal to the change in momentum of the baseball:
where we have
m = 0.144 kg is the mass of the ball
v = -47 m/s is the final velocity of the ball
u = 42 m/s is the initial velocity of the ball
Substituting into the equation, we find
And since we are interested in the magnitude only,
(b) 2.78 kN
The impulse exerted on the ball is also equal to the product between the average force and the contact time:
where
F is the average force exerted on the ball
is the contact time
Solving the formula for F, we find
(c) The force exerted on the ball is much larger (1988 times more) than the weigth of the ball
The weight of the ball is given by
where
m = 0.144 kg is the mass of the ball
g = 9.8 m/s^2 is the acceleration due to gravity
Solving the equation for W, we find
So as we see, the force exerted on the ball (2783 N) is almost 2000 times larger than the weight of the ball (1.4 N):