瞬时速度公式
速度定义为其位置相对于其参考系的变化率。它是一个向量,因为它具有大小和方向。速度的 SI 单位是米每秒或 m/s。而速度测量物体随时间变化的距离。它有大小但没有方向,因此是一个标量。速度的 SI 单位是米每秒或 m/s。
瞬时速度简介
瞬时速度定义为物体在特定时刻的速度。它是速度的大小。它是特定时刻的实际速度。随着时间趋近于零,物体行进的距离也趋近于零。它是距离时间比的非零极限。就图形而言,瞬时速度是旅程中任何点的切线斜率。
瞬时速度公式:
根据公式,瞬时速度是距离与时间的比值。
Speed(i) = limdt->0 ds/dt
where,
Speed(i) = Instantaneous speed
ds = Distance traveled
dt = Time interval
瞬时速度可以通过一个物体在很短的时间间隔内经过的最短距离来计算。我们还可以通过确定位置与时间图的斜率来计算它。
瞬时速度单位
瞬时速度的 SI 单位是米每秒或 m/s。瞬时速度的 CGS 单位是 cm/s。它是一个标量,因为它有大小但没有方向。
平均速度和瞬时速度之间的差异
Average Speed | Instantaneous Speed |
Average speed is defined as the total distance travelled divided by the total elapsed time. | Instantaneous speed is defined as the speed at a particular instant of time. |
Formula: Total distance / Total time | Formula: The distance at that instant / Time at that instant. |
It is measured by calculating the speed for an entire journey | It is measured with the help of a speedometer. |
It is always constant. | It is not constant. |
Example: A bike travelling with a speed of 40 miles/hour; thus, the average speed is 40 miles in an hour | Example: A bike travelling at a certain speed at an instant of time can be given by a speedometer. |
瞬时速度和瞬时速度之间的差异
Instantaneous Speed | Instantaneous Velocity |
Instantaneous speed is the magnitude of instant velocity at a given instant of time | Instantaneous velocity is the change of position that takes place at a very small interval of time |
It is a scalar quantity. | It is a vector quantity. |
Formula: Speed(I) = ds/dt | Formula: Vi = lim∆t→0 ds/dt |
Unit: Meters per second (m/s) | Unit: Meters per second (m/s) |
示例问题
问题 1:计算一个物体在 t=8s 时通过函数x(t) = 5t 3 – 16t +100 m 的瞬时速度。
解决方案:
Given:
x(t) = 5t3 – 16t +100 m
t = 8s
Sinst = limt->T (dx/dt)
= limt->8 d[x(t)]/dt
= limt->8 d[5t3 – 16t + 100] / dt
= limt->8 [15t2 – 16]
= 15(8)2 – 16
= 15(64) – 16
Sinst = 944 m/s
问题 2:望远镜拍摄流星在 0.001 秒内行进 100 公里的照片。在拍照的那一刻,这颗流星的瞬时速度是多少?
解决方案:
In the very short time duration, the instantaneous speed of the meteor will be given by:
Speed = Distance/Time
= 100 km/0.001 seconds
= 1,00,000 km/seconds.
问题3:一个球被抛向空中。它一直向上移动,然后在时间 t = a 个单位,它停止向上移动并开始向下移动。在 t = a 个单位时,球的瞬时速度是多少?
回答:
At the instant of t = a units, the instantaneous speed of the ball will be zero as the ball stops and then starts its journey downwards under the force of gravity.
问题4:当物体落下并受重力作用时,其位置根据函数x(t) = 4.9t 2变化,x(t) 以米为单位。 t = 2.5 s 时的瞬时速度是多少?
解决方案:
Given:
x(t) = 4.9t2
t = 2.5 s
Find the instantaneous speed by using the formula:
Sinst = limt->T (dx/dt)
= limt->2.5 d[x(t)]/dt
= limt->2.5 d[4.9t2] / dt
= limt->2.5 [9.8t]
= 9.8(2.5)
= 24.5 m/s
问题 5:计算一个物体在 t = 2s 时通过函数x(t) = 2t 2 + t + 10 cm 的瞬时速度。
回答:
Given:
x(t) = 2t2 + t + 10 cm
t = 2s
Sinst = limt->T (dx/dt)
= limt->2 d[x(t)]/dt
= limt->2 d[2t2 + t + 10] / dt
= limt->2 [4t + 1]
= 4(2) + 1
Sinst = 9 cm/s