Velocity describes how position changes; acceleration describes how velocity changes. Two layers of change!
Log in Danielmclean.goose 8 years agoPosted 8 years ago. Direct link to Danielmclean.goose's post “Can't something change di...” Can't something change direction and not be accelerating?? • (55 votes) Derek Schuerman 8 years agoPosted 8 years ago. Direct link to Derek Schuerman's post “an alternative way of thi...” an alternative way of thinking about it would be if velocity equals rate x direction, if you change any variable in that it would change the velocity, which is the definition of acceleration. (16 votes) laddhanishtha 7 years agoPosted 7 years ago. Direct link to laddhanishtha's post “Can someone please give t...” Can someone please give the correct answers for the car exercise? I don't understand the explanation. and what is exactly meant by flooring in? • (34 votes) Mursi Serag 7 years agoPosted 7 years ago. Direct link to Mursi Serag's post “Quite late, but "flooring...” Quite late, but "flooring it" does refer to suddenly speeding up, and applies especially to cars- It stems from the fact that (at least in older cars) the lower you press the gas pedal the faster the vehicles goes. Ergo, flooring the gas pedal would cause the car to take off at full speed. (12 votes) Steph 7 years agoPosted 7 years ago. Direct link to Steph's post “Could someone re-explain ...” Could someone re-explain the picture with the four cars? I'm not quite sure about why the car slows down if the signs of velocity and acceleration are oppposite and why it speeds up when they have the same signs. Someone please help? • (8 votes) Good, clear question. Maybe this helps... F=ma right? so if they are equal, they are in the same direction. Kinda makes sense I guess: if you push something, it will accelerate in that same direction. Does that help or no?? (12 votes) RobinZhangTheGreat 8 years agoPosted 8 years ago. Direct link to RobinZhangTheGreat's post “So when we accelerate, we...” So when we accelerate, we feel as if a force was dragging us backwards and let us feel the inertia. Can we use this principle to make some thing which measures acceleration? • (7 votes) T XY 8 years agoPosted 8 years ago. Direct link to T XY's post “Probably no. And the fo...” Probably no. And the force that drag us backward IS inertia. (Sorry if I'm mistaken. You seemed to treat inertia and 'the force that drag us backwards' as a separate thing.) Inertia is the tendency of an object to remain in its state. For example, a rolling ball will continue rolling in a straight line due to its inertia unless compelled by an external force. (friction, gravity, somebody kicking it etc) Same thing, inertia keeps a ball stationary unless someone apply force on it. Well, inertia is a measure of mass though. Hopes this helps. (12 votes) meve2001 9 years agoPosted 9 years ago. Direct link to meve2001's post “What is the main or basic...” What is the main or basic difference between speed and velocity? Acceleration is used only for change in velocity or even for a change in speed? • (3 votes) robshowsides 9 years agoPosted 9 years ago. Direct link to robshowsides's post “Speed is the magnitude of...” Speed is the magnitude of velocity. Velocity is a vector, which means it has two parts: first, your velocity has a magnitude, which just answers the question "how fast?", but does not say anything about the direction the object is moving. The second part of velocity is its direction, which answers the question "which way?". So a velocity might be "20 m/s, downward". The speed is 20 m/s, and the direction is "downward". Acceleration is the rate of change of velocity. Usually, acceleration means the speed is changing, but not always. When an object moves in a circular path at a constant speed, it is still accelerating, because the direction of its velocity is changing. (17 votes) Jericho Tuadles 7 years agoPosted 7 years ago. Direct link to Jericho Tuadles's post “out of curiosity. While s...” out of curiosity. While slowing down, why should it be called as negative acceleration rather than deceleration? • (11 votes) DeadshotJoeZ 14 days agoPosted 14 days ago. Direct link to DeadshotJoeZ's post “Essentially, both mean th...” Essentially, both mean the same thing, however since acceleration is a vector quantity, in classical physics all vector quantities are either positive or negative. So we write negative acceleration. (1 vote) Tyler Reiss 8 years agoPosted 8 years ago. Direct link to Tyler Reiss's post “I don't understand: How d...” I don't understand: How does -34m/s+8m/s^2(3s)= -10m/s? • (3 votes) Seth Reine 8 years agoPosted 8 years ago. Direct link to Seth Reine's post “Your current velocity is ...” Your current velocity is 34 m/s in the opposite direction of what is considered the "positive" direction, so it is -34 m/s. Acceleration, 8 m/s^2, is the change in velocity, and in this case it is in the positive direction. So, the velocity will become 8 m/s more positive for every second that this acceleration is present. (8 m/s^2)*(3s)=24 m/s, This is a positive change in velocity, so -34 m/s + 24 m/s=-10 m/s. You are still moving in the opposite direction but at a slower magnitude. (8 votes) alan bell a year agoPosted a year ago. Direct link to alan bell's post “If i'm traveling east at ...” If i'm traveling east at 20 mph in my toyota camry and got bored with the traffic and changed lanes at 25 mph to my right of the car in front of me, is'nt that changing velocity on a positive? • (4 votes) Charles LaCour a year agoPosted a year ago. Direct link to Charles LaCour's post “It all depends on what di...” It all depends on what directions you assign to positive direction of your axis, if it is in the positive direction then is it positive. (3 votes) Bay Bay 7 years agoPosted 7 years ago. Direct link to Bay Bay's post “how do u determine if the...” how do u determine if the acceleration is positive or negative? • (2 votes) Andrew M 7 years agoPosted 7 years ago. Direct link to Andrew M's post “Just look at the directio...” Just look at the direction of the CHANGE in velocity. If the change is toward the positive direction, it's positive. (4 votes) swaraak07 a year agoPosted a year ago. Direct link to swaraak07's post “how do we know which is p...” how do we know which is positive or negative direction when the origin point is not given ? • (3 votes) Aaron a year agoPosted a year ago. Direct link to Aaron's post “Generally, the right side...” Generally, the right side is indicated as the positive direction whilst the left side as the negative direction. (3 votes)Want to join the conversation?
Actually, the first two pictures where the velocity is positive is quite simple to get, but the cases that confuse me the most are the ones in which the velocity is negative.
So, if you are ok with that idea, think about the acceleration arrow (vector) in your diagrams as being replaced or equal to the force vector.
And to correspond to your given example, I think the bus and passenger situation will be a better explanation:
Passengers tend to move backwards when a bus accelerates. This is because the inertia in their body keep them at rest. So, passengers will lean backwards when the bus moves forward.
