Chapter 4: Problem 44
Find expressions for the force needed to bring an object of mass \(m\) from rest to speed \(v\) (a) in time \(\Delta t\) and (b) over distance \(\Delta x\).
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Chapter 4: Problem 44
Find expressions for the force needed to bring an object of mass \(m\) from rest to speed \(v\) (a) in time \(\Delta t\) and (b) over distance \(\Delta x\).
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A subway train's mass is \(1.5 \times 10^{6} \mathrm{kg} .\) What force is required to accelerate the train at \(2.5 \mathrm{m} / \mathrm{s}^{2} ?\)
A truck crashes into a stalled car. A student trying to explain the physics of this event claims that no forces are involved; the car was just "in the way" so it got hit. Comment.
A \(74-\mathrm{kg}\) tree surgeon rides a "cherry picker" lift to reach the upper branches of a tree. What force does the lift exert on the surgeon when it's (a) at rest; (b) moving upward at a steady \(2.4 \mathrm{m} / \mathrm{s}\) (c) moving downward at a steady \(2.4 \mathrm{m} / \mathrm{s} ;\) (d) accelerating upward at \(1.7 \mathrm{m} / \mathrm{s}^{2} ;\) (e) accelerating downward at \(1.7 \mathrm{m} / \mathrm{s}^{2} ?\)
A \(2.50-\mathrm{kg}\) object is moving along the \(x\) -axis at \(1.60 \mathrm{m} / \mathrm{s} .\) As it passes the origin, two forces \(\vec{F}_{1}\) and \(\vec{F}_{2}\) are applied, both in the \(y\) -direction (plus or minus). The forces are applied for \(3.00 \mathrm{s}\), after which the object is at \(x=4.80 \mathrm{m}, y=10.8 \mathrm{m} .\) If \(\vec{F}_{1}=15.0 \mathrm{N}\) what's \(\vec{F}_{2} ?\)
Starting from rest and undergoing constant acceleration, a \(940-\mathrm{kg}\) racing car covers \(400 \mathrm{m}\) in 4.95 s. Find the force on the car.
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