Scelta multipla
In introductory physics, the use of force to move an object through a displacement is called what quantity?
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9. Work & Energy
Intro to Calculating Work
Scelta multipla
You push a 3kg box against a wall for a distance of 2m with a force of 40N that makes a 53° angle with the horizontal, as shown. Calculate the work done by gravity.
A
58.8 J
B
-58.8 J
C
- 160 J
D
-80 J
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Identify the force of gravity acting on the box. The force of gravity (weight) is given by the formula: F_gravity = m * g, where m is the mass of the box (3 kg) and g is the acceleration due to gravity (approximately 9.8 m/s^2).
Calculate the force of gravity: F_gravity = 3 kg * 9.8 m/s^2.
Determine the direction of the gravitational force. Gravity acts vertically downward, while the box is pushed horizontally against the wall.
Since the gravitational force acts perpendicular to the direction of the displacement (horizontal), the work done by gravity is calculated using the formula: Work = F * d * cos(θ), where θ is the angle between the force and the direction of displacement. Here, θ = 90°.
Calculate the work done by gravity: Work = F_gravity * 2 m * cos(90°). Since cos(90°) = 0, the work done by gravity is zero.
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