Answer:
t=7.33 s
Explanation:
According to Newton's second law:
because we don't want the box to slide, the acceleration has to be zero.
we know that:
Now having the acceleration, we can use the following formula.
Arun places a beaker of water on a hotplate and turns the hotplate on. The temperature in the room is 25 ºC. After the water hea
1 answer:
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a) The work done is 920 J
b) The work done is 5200 J
Explanation:
a)
In this first part of the problem, the crate is moved horizontally at constant speed.
The work required in this case is given by
where
F is the magnitude of the force applied
d is the displacement of the crate
is the angle between the direction of the force and of the displacement
Here the crate is moved at constant speed: this means that the acceleration of the crate is zero, and so according to Newton's second law, the net force on the crate is zero: this means that the force applied, F, must be equal to the force of friction (but in opposite direction), so
F = 230 N
The displacement is
d = 4.0 m
And the angle is , since the force is applied horizontally. Therefore, the work done is
b)
In this case, the crate is moved vertically. The force that must be applied to lift the crate must be equal to the weight of the crate (in order to move it a constant speed), therefore
F = W = 1300 N
The displacement this time is again
d = 4.0 m
And the angle is , since the force is applied vertically, and the crate is moved also vertically. Therefore, the work done on the crate this time is
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The final velocity of the skater is 2.34 m/s forward
Explanation:
We can solve this problem by using the law of conservation of momentum. In fact, the total momentum of the system before and after the ball is thrown must be conserved, in absence of external forces.
Before the ball is thrown, the total momentum is:
where
M = 61 kg is the mass of the skater
m = 4.0 kg is the mass of the ball
u = 2.5 m/s (forward) is the combined velocity of the skater and the ball
After, the ball is thrown at twice the velocity, so the final total momentum is
where
V is the final velocity of the skater
v = 2(2.5) = 5.0 is the final velocity of the ball
Since the total momentum must be conserved, we can write
So, the skater is moving at 2.34 m/s (forward) after the shot.
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