Knowing the sign of the work done on an object is a crucial element to understanding work. Positive work indicates that an object has been acted on by a force that tranfers energy to the object, thereby increasing the object's energy. Negative work indicates that an object has been acted on by a force that has reduced the energy of the object.

a. Is the work done on the box by the force of the push positive, negative, or zero?
b. Is the work done on the box by the normal force positive, negative, or zero?
c. Is the work done on the box by the force of friction positive, negative, or zero?
d. Is the work done on the box by gravity positive, negative, or zero?
e. It's time to rearrange your furniture. You try to push your chest of drawers, with a of weight 3,500 N , across the floor to a spot 5 m away. You push as hard as you can for several seconds until you collapse from exhaustion, but the chest does not move. How much work did you do on the chest?
f. A block with mass m slides down a frictionless ramp that is inclined at an angle ϕ above the horizontal. How much work is done on the box by gravity if the box moves a distance d down the slope?
g. Assume that Earth's orbit around the sun is circular. How much work is done on the Earth by the Sun in one complete orbit? The mass of the Earth is Me, the mass of the Sun is Ms, and the distance from the Sun to the Earth is res
h. A rock with mass m is pressed up against a spring with spring constant k , compressing it by x from its relaxed position. How much work is done on the rock by the spring?

a) W > 0

b) W = 0

c) W < 0

d) W = 0

e) W = 0

f) W = m*g*Sin ϕ*d

g) W = - k*x²/2

Explanation:

a. Is the work done on the box by the force of the push positive, negative, or zero?

The work done on the box by the force of the push is positive

W > 0.

The box has been acted on by a force that tranfers energy to the box, thereby increasing the object's box.

b. Is the work done on the box by the normal force positive, negative, or zero?

The work done on the box by the normal force is zero.

W = 0  since ϕ = 90° ⇒ Cos 90° = 0

c. Is the work done on the box by the force of friction positive, negative, or zero?

The work done on the box by the force of the push is negative

W < 0.

The box has been acted on by a force that has reduced the energy of the box.

d. Is the work done on the box by gravity positive, negative, or zero?

The work done on the box by gravity is zero.

W = 0  since ϕ = 270° ⇒ Cos 270° = 0

e. It's time to rearrange your furniture. You try to push your chest of drawers, with a of weight 3,500 N , across the floor to a spot 5 m away. You push as hard as you can for several seconds until you collapse from exhaustion, but the chest does not move. How much work did you do on the chest?

W = 0 since the displacement is zero (d = 0).

f. A block with mass m slides down a frictionless ramp that is inclined at an angle ϕ above the horizontal. How much work is done on the box by gravity if the box moves a distance d down the slope?

W = m*g*Sin ϕ*d

g. Assume that Earth's orbit around the sun is circular. How much work is done on the Earth by the Sun in one complete orbit? The mass of the Earth is Me, the mass of the Sun is Ms, and the distance from the Sun to the Earth is res

W = 0 since ϕ = 90° ⇒ Cos 90° = 0

h. A rock with mass m is pressed up against a spring with spring constant k, compressing it by x from its relaxed position. How much work is done on the rock by the spring?

W = - k*x²/2

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length