What is the resultant of a pair of forces 100N upward and 75N downwards?

25N up

Why is speed scalar and velocity vector?

Speed is only a number.Velocity is speed in a given direction.

What is the end point for:45° for 3 blocks, S for 7

Calculate the resultant for the following:

8m east, 2m north, 6 m west

22+22 = √8 = 2.9m NE

A ball is dropped from a 60m high building. How far will it have fallen after 3.0 seconds?

y = ½ gt2

4.8m/s2 x 9s2 = 44.1m

In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant?

No other forces are involved.

Why does motion in the vertical component change?

Gravity

A bird flies at 20km/h. How long does it take to fly 400km?

400km/ 20km/hr = 20hours

A rock is thrown at a target 40m away. It hits the target in 4.0 seconds. What is the speed of the rock?

40m/4.0 seconds = 10m/s

A stone is dropped from a bridge and hits the ground after 4.0 seconds. How high is the cliff?

y = ½ gt2

4.8m/s2 x 4.0s2 = 78.4m

A salmon jumps up a waterfall to return home to spawn. The waterfall is 2.0m high. What minimum speed must the fish meet to jump the waterfall?

vf2 = vyo

2 + 2a d∙

= 6.26m/s

What is the resultant path of a ship traveling north at 8m/s if the tide is pushing at 2m/s east. What is the angle?

82m/s + 22m/s = √68m2/s2= 8.2m/s8/2 tan-1 = 76°

A rock is dropped and hits bottom 5 seconds later. What is its velocity just before it hits bottom.vy = vyo + ayt

9.8m/s2 x 5 s = 49m/sWhat is the height of the cliff?y = ½ gt2 = 4.9m/s2 x 25 s2 = 122.5m

A rock is thrown from a cliff at 20m/s. What is the horizontal velocity after 2.0 seconds?20m/sWhat is its vertical velocity in 2.0s?y = ayt 9.8m/s2 x 2.0 s = 19.8m/s

A rock is thrown from a cliff at 20m/s. What is its horizontal displacement after 3.0s?x = vxi t = 20m/s x 3.0s = 60m

• A man shoots a gun at 2m above ground. The bullet is fired and hits the ground 1000m away. What vertical velocity did the bullet hit the ground?• vfy

2 = voy2 + 2a x d

• 2(9.8m/s2) x 2m = vfy2

• √39.2m2/s2 = 6.26m/s

• A ball is projected horizontally from a point 245m above the ground. How long does it take to reach the ground?• y = ½ gt2

• t2 = y ÷ ½ g• 245m ÷ 4.9m/s2 = √50s2

• = 7.07 seconds

• A ball is projected horizontally from a point 245m above the ground. How long does it take to reach the ground? = 7 seconds (previous slide)

• If the ball strikes 49m horizontally from the point of projection, what is the horizontal velocity?• v = d/t 49m/7s = 7m/s

• A projectile is shot upward at a 60° angle from the ground at 60m/s. What is the vertical component of velocity?

• y = 60m/s (sin 60°) = 52m/s

• What is its horizontal component of velocity?• vx= v (cos Ө)

• vx = 60m/s (cos 60°) = 30m/s

• How far in the x direction has it gone in 3 seconds?• x = vt 30m/s x 3 seconds = 90m