optics

Two cyclists X and Y are separated by a distance of 68 km. At t = 0, X starts cycling with speed 8.0 km h^-1 , and one hour later Y starts cycling with speed 12 km h^-1 . What is the displacement of Y when X and Y meet?

• 32 km

• −32 km

• 36 km

• −36 km

A small plane takes off at a speed of 30 m s⁻¹ after accelerating from rest on a runway for 900 m. What is the acceleration of the plane on the runway?

• 0.50 m s⁻²

• 1.0 m s⁻²

• 3.0 m s⁻²

• 4.0 m s⁻²

A block accelerating on a straight line with constant acceleration a increases its speed from u to v in a time t. The following are suggested expressions for the displacement of the block during this time: I v^2 − u^2 / 2a II ut + 1/2 a t^2 III vt − 1/2 a t^2 Which of the following are correct expressions for the displacement?

• I and II

• I and III

• II and III

• I, II and III.

A ping-pong ball is released from rest and falls vertically. The ball attains terminal speed. Which graph shows the variation of the position of the ball with time?

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On Earth, a stone takes time T to fall from rest a certain vertical distance and impacts the surface with speed v. What would the time of fall and impact speed be when the stone falls the same vertical distance on a planet where the acceleration of free fall is g/4?

• 2T, v/2

• 2T, v/4

• 4T, v/2

• 4T, v/4

On Earth the magnitude of the acceleration of free fall is g=9.8 m.s⁻². A ball is thrown upwards and after reaching its maximum height falls down again. Taking the upward direction as positive, what is correct about the acceleration of the ball during its motion?

• A

• B

• C

• D

A projectile is launched horizontally from a vertical cliff with a speed 30 m s⁻¹. The cliff is 80m high. How far from the base of the cliff does the projectile land?

• 240 m

• 120 m

• 90 m

• 80 m

A projectile is launched horizontally from a cliff and hits the ground 5.0 s later. How high is the cliff?

• 125 m

• 75 m

• 50 m

• Cannot be determined without knowing the launch speed.

A projectile is projected at 45° to the horizontal with kinetic energy K. What is the kinetic energy of the projectile at the highest point of its path?

• 0

• K/4

• K/2

• K/√2

A projectile is projected at 45° to the horizontal. The magnitude of its momentum at launch is p. What is the magnitude of its momentum at the highest point of its path?

• 0

• p/4

• p/2

• p/√2