Motion

Speed and Velocity

An object is moving if its position changes against some background that stays the same◦Reference frame

Speed and Velocity

Speed describes how fast an object moves

How do we determine speed?

Speed and Velocity

To find speed, you must measure two quantities: distance traveled and the time it takes to travel that distance

Speed and Velocity

When an object covers equal distances in equal amounts of time, it is moving at a constant speed

Speed and Velocity

The relationship between speed, distance, and time can be investigated by plotting a distance-time graph

Speed and Velocity

Most objects do not move at constant speed

Average speed is the distance covered divided by the time it takes to travel that distance

Speed and Velocity

Velocity describes both speed and direction

Speed and Velocity

1. 110m/72s=1.5 m/s toward shore

Speed and Velocity

1. 110m/72s=1.5 m/s toward shore2. 38m/1.7s= 22m/s toward first base

Speed and Velocity

1. 110m/72s=1.5 m/s toward shore2. 38m/1.7s= 22m/s toward first base3. D=vt (12km/h)(5h)=60km(1000m/km)=

6x104 m

Speed and Velocity

1. 110m/72s=1.5 m/s toward shore2. 38m/1.7s= 22m/s toward first base3. D=vt (12km/h)(5h)=60km(1000m/km)=

6x104 m4. T=d/v (2.6km)(1000m/km)/(28m/s)=93s

Speed and Velocity

The velocity of an object changes if its speed or direction changes or both change

Momentum

An object with more momentum would be more difficult to stop◦Depends on both its

velocity and its mass

Momentum

For an object moving in a straight line:◦Momentum=

mass x velocity P=mv

Momentum

Momentum, like velocity, has direction◦Momentum has

same direction as velocity

If an object is not moving, its momentum is zero

Momentum

1.a. (75kg)(16m/s)=1200kg m/s forward

Momentum

1.a. (75kg)(16m/s)=1200kg m/s forward b. (135kg)(16.2m/s)=2190kg m/s north

Momentum

1.a. (75kg)(16m/s)=1200kg m/s forward b. (135kg)(16.2m/s)=2190kg m/s north c. (5kg)72m/s)=360kg m/s eastward

Momentum

1.a. (75kg)(16m/s)=1200kg m/s forward b. (135kg)(16.2m/s)=2190kg m/s north c. (5kg)72m/s)=360kg m/s eastward d. (.8kg)(6.5m/s)=5kg m/s to the left

Momentum

1.a. (75kg)(16m/s)=1200kg m/s forward b. (135kg)(16.2m/s)=2190kg m/s north c. (5kg)72m/s)=360kg m/s eastward d. (.8kg)(6.5m/s)=5kg m/s to the left e. (48.5kg)(0m/s)=0kg m/s

Momentum

The total amount of momentum in a system is conserved