17.4 - Spaced practice A level Physics

A bob of mass 0.50 kg is suspended from the end of a piece of string 0.45 m long.

The bob is rotated in a vertical circle at a constant rate of 120 revolutions per minute.

What is the tension in the string when the bob is at the bottom of the circle?

• 5.8 N

• 31 N

• 36 N

• 40 N

A car exerts a driving force of 500 N when travelling at a constant speed of 72 km h^–1 on a level track. What is the work done in 5 minutes?

• 3.0 × 10⁶ J

• 2.0 × 10⁶ J

• 2.0 × 10⁵ J

• 1.1 × 10⁵ J

What is represented by the area under a force–displacement graph?

• rate of change of kinetic energy

• change in momentum

• work done

• acceleration

A ball of mass 0.30 kg is attached to a string and moves in a vertical circle of radius 0.60 m at a constant speed of 5.0 m s^–1.

Which line, A to D, in the table gives the correct values of the minimum and maximum tension in the string?

• A

• B

• C

• D

A rocket of mass 12 000 kg accelerates vertically upwards from the surface of the Earth at 1.4 m s⁻².

What is the thrust of the rocket?

• 1.7 × 10⁴ N

• 1.7 × 10⁵ N

• 1.3 × 10⁵ N

• 1.6 × 10⁵ N

A stone of mass 0.4 kg is projected horizontally at a speed of 6.0 m s⁻¹ from the top of a wall, 5.0 m above the surrounding ground. When it arrives at the ground its speed is 10 m s⁻¹.

How much energy is lost by the stone in falling through the air?

• 2.4 J

• 6.8 J

• 12.8 J

• 14.4 J

Answer explanation

Firstly, use suvat to find the speed at which the stone should have hit the ground (be careful with signs!), then find the difference in their kinetic energies

A 0.20 kg mass is whirled round in a vertical circle on the end of a light string of length 0.90 m.

At the top point of the circle the speed of the mass is 8.2 m s^–1. What is the tension in the string at this point?

• 10 N

• 13 N

• 17 N

• 20 N