# Why is the magnitude of its acceleration less on the descent

• katana
In summary, the conversation discusses the concept of a block sliding up and down a ramp and why its acceleration is less on the descent than on the ascent. The reason for this is due to the direction of friction forces, which always act to oppose slipping between surfaces. The conversation also suggests analyzing the situation in terms of Conservation of Energy or resolving the forces acting on the block.
katana
This is sort of a concept problem.
It says: A block is given a push so that it slides up a ramp. AFter the block reaches its highest opint, it slides back down. Why is the magnitude of its acceleration less on the descent than on the ascent?

I know it as to do with friction but I don't see how the friction forces are different on the ascent and the descent.

Here's a hint: Friction always acts to oppose slipping between surfaces. So... when the block slides up the ramp, which way is it slipping with respect to the ramp surface? So which way must friction act? Do the same analysis for the block sliding down the ramp. Then compare total force on the block in both cases.

You could also try to analyse it in terms of Conservation of Energy if you want. When you initially give the box a push, the box will use up its kinetic energy to gain GPE and do work against friction. Afterwards, the GPE will be used to do work against friction again and give the box kinetic energy to reach the bottom.

Another way of tackling this is to resolve the forces acting on the box, which you will find:
Going up: mg sin @ + friction (both downwards)
Going down: mg sin @ (downwards) - friction (upwards)

## 1. Why is the magnitude of acceleration less on the descent?

The magnitude of acceleration is less on the descent because of the influence of gravity. As an object falls, it experiences a constant acceleration due to the force of gravity. This acceleration is directed towards the center of the Earth, causing the magnitude to decrease as the object gets closer to the surface.

## 2. How does air resistance affect the magnitude of acceleration during descent?

As an object falls, it experiences air resistance which is a force that opposes its motion. This force increases as the object's velocity increases, eventually reaching a point where it is equal to the force of gravity. At this point, the object will reach its terminal velocity and the magnitude of acceleration will decrease to zero.

## 3. Does the mass of the object affect the magnitude of acceleration on descent?

Yes, the mass of an object does affect the magnitude of acceleration on descent. According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Therefore, a heavier object will experience a smaller magnitude of acceleration compared to a lighter object.

## 4. Why is the magnitude of acceleration greater on the ascent compared to the descent?

The magnitude of acceleration is greater on the ascent compared to the descent because of the additional force of thrust or propulsion. During the ascent, a rocket or aircraft is actively pushing against the force of gravity, resulting in a higher magnitude of acceleration. On the descent, there is no additional force pushing against gravity, causing the magnitude of acceleration to decrease.

## 5. How does the angle of descent affect the magnitude of acceleration?

The angle of descent does not directly affect the magnitude of acceleration. However, it can affect the components of acceleration, such as the horizontal and vertical components. For example, if an object is descending at an angle, the magnitude of acceleration will be divided into a horizontal and vertical component, with the vertical component being affected by the force of gravity and the horizontal component being affected by other forces such as air resistance.

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